I can give you a really good and long answer, I will give you some links of things to try and worksheets too ('self-help' stuff). You will probably never use it but that is ok.... I will still provide it.
But are you male or female? Your question never said, it felt a tad on the male side. But that is just a guess. It realistically never goes away. I am unaware of anyone who has cured it by the time they were a senior. But you learn to manage (like you said) and maintain. Social Phobia or problems like you described are often caused by C-PTSD, PTSD, BP(Bipolar), Borderline (BPD) or other things. Any trauma, perceived negative social experiences or abuse? If you do not remember any chance? If not great it is easier to 'manage'.
These things even gender matter tremendously. Brains are different neurochemically and structurally (size and shape). The illnesses I described change your brain. So know specifically whats wrong or having a great guess is important too.
EDIT:
First thing is BPD is the most difficult illness we know of. It impacts women much more severely than men. If you believe in such things it also impacts gifted/empathic women worse. If not HSPs worse, you can google that term, I guess. In most cases where their is repetitive trauma women have numerous co-occurring symptoms: Social Phobia, Psychosis, fear of abandonment which is out of control, MDD (Depression) and dissociation (you can google that). With repetitive ("Chronic") trauma especially for women who are still in negative environments not getting regular 'good' treatment (self guided or other). Usually C-PTSD is very common:
https://www.goodtherapy.org/blog/what-do-cptsd-and-borderline-personality-have-in-common-0628194
That is good you did the talent show. It just feels good to get attention sometimes. It shows you care, want to work on yourself (probably) and will push even if it is bad/tough. Many women just cry and give up. Generally people suck - they just do. Often women are worse than males. But both are tough.... Petty, jealous, competitive, self centered or just rude. They belittle others. They form groups and push others away. They push people who are not in their group away more forcefully. The smaller they make you feel the bigger and better they feel. Often if the person does nothing, they push harder. It must be tough and tiring to explain yourself over and over. It is a tiring and draining thing. Though 100 + times worse for you. People also give off "energy", Think of it spiritually or scientifically. You pick up signs, signals, attitude, emotion/anger, discomfort of them. A woman with BPD is much better at reading and picking up this energy. People are generally negative unless you kiss their %$#%^ or are in their group/crew.
Come on? Are you kidding? You wonder why you do not trust people? People are the primary cause of your issues. You never asked for any of this, to feel like this. It is your teachers job, not yours to see you are uncomfortable and they should help. It is your boyfriends, friends or parents. Often people just do not care to understand or help - it is easier to push away then they impress friends or others too. An example if someone in a wheelchair asks you to pick up a pencil for them you do not ignore, belittle or not help. You have an illness/concern too. The fact the teacher does not care or is not doing more is not ok. It is a bit scary.
You are probably too stubborn to believe or accept this. But a lot of the problem is "external influencers". People are abandoning, ignoring, invalidating or just not caring to understand. It is a lot of negative experience/"energy". DBT (something you should look into and probably know - Dialectic Behavior Therapy). It teaches us mindfulness, radical acceptance and a dozen other things. Whether it is guardians or this teacher, you have to pull away from them - there is probably good reason you do not like them.
Hypervigilance - google/research it is another reason this is happening
Your neurochemistry and brain literally changed and its not your fault, blame you - I do not care. But it is not. Try to read this: https://www.psychiatrictimes.com/special-reports/neurobiology-borderline-personality-disorder
The way you experience/feel or process and analize external signals ('energy'/emotion) from others is a bit different. Its a whirlwind, intense and often out of control. An endless roller coaster. 'Emotional Dysfunction' changes your 'emotive response' - how you interact or react to energy/situation or external influencers (people).
The mechanisms which limit or control fear with others are removed for yours. You are still associating past interactions with negative people to new interactions (see that neurobiological link above). Technically it is 'trauma memories' / hot spots. These are sometimes full blown flashbacks or just feelings in your body.
Blood flow in your brain is increased which probably means your blood pressure and other things increase. This causes a "STARTLE REFLEX" (research it) making you jumpy/jerky. Higher blood pressure causes or allows panic quicker and makes you shaky/trembly a bit.
Those are a few reasons things happen, there are lots. What do you do? Realize you can not control other people, pull away a bit, look for people who just get you 2-3 is an ok start. You learn about DBT and CBT and how they have helped with BPD or C-PTSD. If your guardians are not helping. If they are loud, angry or harmful you need to pull away from them too. Not run away but a bit more emotionally distant. You are not stupid all that negative action or energy is very bad - it caused your current problems. EFT/Tapping often helps especially if you are open to spirituality (research it "EFT/Tapping"). You need to address some of the past problems eventually. Right now you have problems with "experiential avoidance" (research that with C-PTSD/BPD). A holistic approach is demonstrably the best option for a women like you. Meaning mind/body approach more than just seeing a GP/Doctor. If you are on lots of pharmaceuticals giving you side effects try to get off them.
You can probably be pretty mean, rude, "Snappy" or stubborn at times. The #1 thing is you need a person who understands BPD and the other problems. Someone to help you plan and push when needed even if you are having a bad day. Often a friend isn't great for this because there is too much emotion. It does not have to be a therapist just someone you know. Talking/crying to someone who won't leave who just listens and helps is important (psychotherapy).
You might want to look into "imaginal therapy" which is an 'ET' module. A few of the right herbs: CBD; or dozens of things ('nootropics), some CBT work sheets[research DBT or CBT BPD worksheets], cutting out negative people or energy the best you can and having those 1-2 people who just listen and help plan. That will really help with panic. You have to learn new, different or better ways to cope, deal with "intrusive thoughts" (ANTS - automatic negative thoughts). You need to do some 'cognitive restructuring'
So, how you feel is ok. It is not normal/typical. Not many people live with what you did. BPD is Emotional Intensity, it notches up your emotions so high, making them so powerful - you drown. Like 3rd degree burns on the skin. What you have to do is impossibly hard. In the USA it is really hard to get proper help too. Especially if you are lower income. It will typically get worse every 3-6 months from 25 + if you do nothing. It is a bit harder to get help in UK regions too.
Hope something there helped. Learning, research, talking, expressing even when it is painful/hard are places you start. You are triggered by bad people/energy or negative situations "flash memories". It should be expected it happens. You reprogram your brain (really). Cut out bad crap in life, focus on good things, stop pharmaceuticals. You be open to trying 100 different things and only continue with the ones you feel work, who cares what others think.
I do not believe you are a junior. You seem too mature. Most women that age just don't look for ways to improve then at 25 cry all day about how they need to die or other defense mechanisms. If you are that is fine who cares what I think. First thing is talk to someone who gets it make a plan research words I wrote about
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