tl;dr how to communicate with my s/o about my sexually traumatic incidents and maintain healthy boundaries when it comes to sex (also emotionally preparing for it)

i (17F) very recently got into a relationship with my bf (19M) and i already have a list of things i need to communicate so he knows what he’s getting into (perhaps a bad habit but that’s besides the big issue)

context: i’ve only begun to understand and remember it but a good potion of my trauma comes from a sexually traumatic incident when i was much younger and one that happened within the last year in an unhealthy relationship 

i realize that i dissociate a lot, if not entirely, when i’m physically present in the situation and lose my ability to give consent or be assertive. and sure that’s the insecure and people pleasing side of me, but also what the other person sees instead of my fear of abandonment and fear that they will hurt me 

i don’t wanna fuck up again this time and i know that my bf is understanding and gentle, but i guess i’m seeking a bit of validation and support? i’m currently doing DBT with my therapist but i haven’t talked to her about sexual trauma yet, but she does know that i’ve been in sexual situations without consent :/

if anyone else that has experienced going through this process, some advice would be very appreciated. just preparing myself emotionally and even physically (my body freezes up and it’s just, a struggle lol) +++ communicating what i’m comfy with