I had intrusive thought that i might cheat my bf. Please help me

I have been dating my boyfriend for 5 years. Since we were 17. We study at the same university in the same specialty. We think that we started dating on October 30, 2019, on that day I asked him to help me with my studies, and it happened that we got drunk and kissed. And so we consider that day as the beginning of our relationship, because after that we did not part and were always together. A week later, on November 12, 2019, my ex-boyfriend wrote to me that he was in town and asked if I wanted to meet him. We broke up a long time ago, but we talked and sometimes even kissed. I told my boyfriend that I was going out with a friend because I was afraid to say that he was my ex. We went out, walked, drank beer, talked while sitting on a bench, and he leaned in to kiss me. I leaned back and we kissed. The kiss was not long, a few seconds. kiss wasn't with passion or something. and at that moment I thought I was doing something wrong, because I seem to have a relationship with my boyfriend, and I stopped. After that, we talked some more, he went home, and I went back to the hostel for students(my boyfriend and I lived in the same hostel). I came to my boyfriend, and did not tell about the kiss, because at that moment I did not feel guilty at all. I don't know, maybe I wasn't sure about relationships, because I've never had a serious relationship before, only some flings, and that's why I thought that my current boyfriend would be the same. And really this kiss mean nothing to me. We continued to relationship with my boyfriend, everything was fine. Then I remembered this incident and felt guilty. 6-7 months after we started dating, I told him about it, I told him in the summer of 2020 when we met, because we hadn't seen each other for 4 months due to the coronavirus and quarantine. I cried a lot and asked for forgiveness, said that this kiss mean nothing. My boyfriend calmed me down and forgave me, we didn't even have an argument, we just continued dating as if nothing had happened. Everything was fine, but after 3 years, in August 2022, I remembered this incident and began to blame myself very much. I considered myself a cheater, unworthy of my boyfriend. I just hated myself. My boyfriend didn't understand, because he didn't think about it at all and didn't understand why I was so worried about it. But the anxiety didn't leave me, later I started having false memories and my OCD. I was thinking "what if there was more than a kiss? what if I forgot something? what if I kissed someone else and my brain erased it from my memory?" and billions of such thoughts. I couldn't eat or sleep, I constantly read about betrayals, I read other people's stories, but I didn't get any better. I went to a psychiatrist and he prescribed me a course of antidepressants, which I took for 9 months, but it didn't help.

I never hid anything from my boyfriend and told him everything honestly. Later, I started blaming myself for the fact that I had many boyfriends in the past, and my boyfriend only had one girlfriend, and he still didn't have sex with her. And I had one sex before we started date with my bf and I felt very ashamed because of it, I considered myself a wh*re and unworthy of him. I am infinitely ashamed of all the bad deeds and thoughts I had about my boyfriend. I love him infinitely, and I want to spend my whole life with him. But my past stupid actions haunt me and I feel extremely guilty about them.

Because of all these thoughts, I went to a psychologist and a psychiatrist for a very long time, I was diagnosed with OCD, because I was constantly worried that I had cheated, that I had done something bad in the relationship, I was constantly looking for some kind of betrayal, I looked in the Google timeline where I was every day, did I definitely not cheat anywhere. It seemed to me that I could not trust myself.

I considered myself the worst girl in the world. I constantly confessed to my boyfriend for my every thought and every action, I had to be crystal clear in front of him. My boyfriend asked me to stop it, he said that he doesn't care what I thought and what I did, he knows that I love him and he loves me. And I really never hid anything from him, not a single thought or action. But I am ashamed of it now. I also had a period when I doubted whether I loved my boyfriend. I also told him about it, because I was afraid that I don't love him, so why should he be with me? But he said that he knew that these were only foolish thoughts, and so they really were. I think I don't deserve my boyfriend, because he is the most perfect person in this world. He is responsive, kind, intelligent, cheerful, loving, understanding. And I am constantly in doubt, constantly on the negative side, and I feel that I will constantly blame myself for those actions for the rest of my life.

Later everything was good and i thought i don't have OCD at all. But no...

Now I've been working at my first serious job for 2.5 months.

I have a mentor who helps me with my work. I always had thoughts when I sit close to a person "what if we kiss and if something happens" but I didn't attach importance to them, I just tried to avoid situations where I can sit close to a man. and one day my mentor sat next to me and we tried to solve the problem (I work in IT). I started having very strong obsessive thoughts. "what if we kiss? what if he gets close to me now and it happens? it will definitely happen. i want him to kiss me. what about my boyfriend? can i cheat on him right now? if he the kissed me I wouldn't push him away. what if i kiss him. What if I put my hand on his and it will be like in the movie. would I betray him if the mentor himself kissed me? If there were all the circumstances, would I cheat? and the answer was yes" . and at the moment seems i want it. This thoughts very scary me. Thought that i might cheat on my bf. And now, I can't get over it. Nothing happened of course, this thought was only in my head while my colleague explain me material.

I don't communicate with my mentor except for work. I don't want to be with him or anything .I have never had such thoughts before that I CAN CHEAT. I was always 100% confident in myself. and when this thought came and I asked myself "could I cheat if he kissed me, would I kiss him back?" and the answer was yes and it just drives me crazy.

Of course i don't want kiss anyone except my bf, i don't want cheat him, this thought appear once when mentor sits next to me that i might cheat.

now I'm afraid that I could betray at that moment.

I don't know what should i do. I really could betray my boyfriend? Or it is just intrusive thoughts? I feel like i already kiss him. I am tired of this thoughts. I know that I don't love my colleague, this is intrusive but it makes me feel like a cheater. I said about this thoughts to my partner. He said to me that i should calm down and it is just a thoughts. For almost 2 years now, my life revolves around the word "cheating".

me and my boyfriend, who knows all about it, can't stand all my thoughts anymore. it is really very hard, and I know how hard it is for him to be with me, a person who is always negative and feels a constant sense of guilt.

Sorry for my bad english and thanks for your opinion

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