Talk to your bf about it and make a plan for how to respond if it happens again. It helped me a lot when I was having flashbacks during intimate moments to have a plan. Ours was that we had an extra safe word for flashbacks that if I said he'd immediately stop what we're doing,give me a blanket to wrap myself in, give me some water, and would start talking about unrelated stuff to distract me. It also really helped having that conversation because every time he apologized while I was panicking it would make it worse, so once he knew and stopped apologizing it shortened how long everything would take

And you can try to look back on all the times you've been triggered during intimacy and see if there's a pattern, so you know what to avoid going forward. But the biggest thing is talking to bf about your feelings and how you two can continue doing things you enjoy without hurting you

Maybe you're being triggered because part of you feels that he is not a safe person. I had that happen with a partner and they turned out to not be a safe person at all so I wouldn't totally brush that off.

Have you ever thought about a sex therapist? If this is a lack of communication or feeling like you are not on the same page, I feel like this is an option. They just treat anything that is sexually related whether it's with a partner or even as an individual which may include performance anxiety or libido (just examples). Google may be able to explain it a bit better than I can. If this is based on some other insecurities or trauma from previous experiences, I recommend a trauma counselor. The way this is written, I'm perceiving this as you are hurt from a previous relationship that you had in February and your pain is being transferred to your current relationship.