Horrendous anxiety over making out with someone else before things got serious

Hi I am a 22 year old female from Australia. I am suffering from seriously severe anxiety over something. My good uni friend asked me out on a date earlier this year (June). I was hesitant because I was unsure we would be compatible and unsure about dating someone in the cohort (we are only 120 people, we see each other all the time), but eventually agreed because I did like him. We went on three dates before I had a trip overseas, the first of which had a little bit of hugging involved and he kissed me at the end of it. However, the second and third were suddenly cold physically (I did not know why), he didn’t hold my hand/put his arm around me/kiss me etc. It was more like hanging out as friends. I was left quite unsure about his feelings for me and we didn't discuss what would happen after I got back from my trip. We never discussed feelings or anything. I then went overseas on a group trip. On this group trip, I met someone I REALLY liked. This guy pulled me aside one night, said he thought I was really cute, and tried to kiss me. I told him I wasn’t sure because I had gone on a few dates with someone before the trip, he asked if we had talked about being exclusive, I said no, so he said it was fine. So we made out, did some second base stuff. Didn’t sleep together. When I got back home, my friend asked me if I wanted to go to the beach to see the sunset. I said I had “sort of caught feelings for someone overseas” and that I didn’t think it was fair to him to continue to see him in this scenario. He was completely fine with this (ostensibly at least) and we continued to be good friends. The guy from the trip lives in my city, we hung out a bit when we got back, but somehow my feelings for him fizzled a bit (perhaps because I realised that he didn’t want to be with me like I had thought, but rather just wanted to get physical with me), and my feelings for my friends suddenly became much stronger than they had ever been in the past. Eventually, 10 weeks after my return to Australia, I asked my friend if he wanted to go on another date after all. We had a chat, I said (again) that I had caught feelings for someone overseas but that my feelings had backflipped… I wasn’t sure if to mention that things had gotten physical, because most people I had asked said I hadn’t done anything wrong, and because I felt that he may have already assumed stuff may have happened, and that if it was a deal-breaker for him, he would ask to make sure. We have now been dating for about 5 weeks (but intensively, sleepovers once or more a week and see each other daily at uni). He hasn’t asked me to be his girlfriend, but I feel like it is assumed at this point since things are very coupley (I also saw him refer to me as his gf to one of his friends on messenger). Everything has really been going great. I really like him and I would be so happy being with him, if it weren’t for the fact that I feel legitimately crippled by the constant thoughts about what happened overseas in my head. Some nights I can’t sleep. I cannot study. I am constantly nauseous. It’s not a matter of how often I think about it, but how often I /don’t/ think about it. Maybe there is a maximum of about 1-2 minutes in a row in a day where I catch myself managing to not be obsessively thinking about this. I have a constant knot in my stomach. Sometimes I wake up okay and then it takes me all of 10 seconds to remember this and feel bad again. It complicates things that I do not know how to feel, because I don’t know if I have done anything wrong. Moreover, I don’t know if not telling him is wrong, even if what I did was not wrong. I feel like a terrible person. Some days I just want to end my life, as dramatic as it sounds, because I (a) feel I do not deserve a life if I do SUCH bad things and (b) want to get rid of the constant physical anxiety I feel. There were a brief few days where I felt better about this after posting on a relationship advice forum and having some reassurance. I felt like a new person. But now the anxiety has returned. I feel like everyone has a different view on what is and isn’t acceptable in the early stages of dating. And I don’t know what his view is?? I don’t know how he would feel if he knew?? I also heard him say to my friend that he doesn’t understand how people stay with people after they cheat, because if you cheat, it’s over. I didn’t think this was cheating, but what if he would? I just don’t know what to do. I want to be with him so badly, but I cannot live with this anxiety. No one could. Maybe I should wait for the anxiety to pass (will it ever?) and assume he knows enough, maybe I should tell him and risk him leaving or ruining the relationship for him, maybe I should just end things (despite it being the best relationship I have ever had minus the anxiety) and move on with my life. Maybe I should wait until one day, a “how many people have you kissed” conversation may inevitably come up… Please help me. I no longer know where to turn or what to do.