A bad decision to have sex is now ruining my life

Please mind the NSFW tag and also TW: includes talk about sexual consent

I (21F, and the other ppl mentioned here are also roughly my age) am a university student and I'm having trouble thinking about my past relationship history. In particular, I hadn't had any sexual relations with people until my sophomore year of college, where I had a friend at the time and I was pressured into sex.

For context, I've been diagnosed with OCD, MDD, and anxiety, and I was in a terrible mental state even before that happened, and unfortunately subjected said friend to a lot of mental breakdowns; this wasn't right of me to do in the first place, but he was kind of an outlet for all my troubles, so I got emotionally attached and didn't let myself blame him for pressuring me into doing something I was so unsure about. I don't want to elaborate on this very much, but my current boyfriend (will refer to as BF to prevent subject misattribution) was only a mutual of this friend at the time, and BF liked me and we got closer as friends, and I eventually developed feelings for BF. But the timeline of this overlapped with what happened with the ex-friend, so BF knows my troubled sexual history with this person, and that is the only person I have been with besides BF. BF taught me what a healthy relationship was and ultimately kind of saved me from the situation I was in and needless to say we now both hate this ex-friend.

I am not someone who is judgmental of people's sexual history, in fact I'm supportive of the autonomy of people's bodies and am also a feminist. So other people's sexual histories mean nothing to me, yet my own is troubling me so deeply because it felt like he took something away from me and I keep spiraling back to this thought even though I have so reason to. BF has made it clear that this doesn't change how he feels about me and he is trying his best to make this less distressing for me, but any time I see people mention stuff related to sex, these bad thoughts keep coming back and make me spiral. I feel that I am gross, and am worried I contracted something (for this I plan on asking for more thorough labs to be done for my own peace of mind, though it's realistically unlikely) and more or less, I just feel constantly haunted.

I want to eventually be able to stop thinking about this, or at least remove all these negative emotions from it, but it's been very hard because it's hard for me to confront in my own head, let alone bring up to my therapist. My therapist knows about all my various other problems related to my mental illnesses, but I'm terrified of talking about this one because I don't want it to affect how she's looked at me. I suppose part of my general OCD is perfection, and everything else I can kind of work on, but this feels permanent and I'm scared.