Hey.
This is VERY common in people who are struggling with trauma histories. Studies have shown that many people have migraines, headaches, and pressure in the front of their head as they deal with the past.
Some theories believe it is stress, while others actually believe that the brain chemicals involved in the trauma memories are stirred up causing pressure as you work-through your past.
Also, you might have some bit of dissociation going on. This is where you feel foggy or dizzy. Dissociation is a spectrum but, the zoning out is common.
ALSO, don't listen to ANYONE who says "let it go"
That is about the most ridiculous thing a person can say. Growing up with trauma, it is impossible to "let it go." It shapes your whole life and changes everything forever.
FYI: When I get out of therapy, I have to take the rest of the day off to take a nap because of the amount of effort and sometimes head pain. It is the hardest thing to overcome, but you are doing it!
Good luck!