I relate to this a lot. I used to dissociate a lot during sex and it took me a while to even just be present in the moment. A big help in this process for me was having a partner who is patient and understanding, even when I can't explain why I'm having problems, but I still feel guilty whenever I flinch from being touched or have to tell her that I'm too overwhelmed to do anything that night. It is worth mentioning that we've been navigating these issues for 6 years without much external guidance, and things have substantially improved just with patience and *communication*. If you're both genuinely committed to meeting each other's needs and are able to clearly and confidently set boundaries with each other, then things can improve, though it may just take time

(I'm sorry if that's not super helpful, just try not to lose hope)