Long post but need help, please 🙏

First of all, I don’t know what I’m doing is right.
I have a great boyfriend of 3 years who is so so dear to me and I absolutely know he’s the one for me.
But 2 years back I met a guy who I have been obsessively thinking about. I had a crush on him which my boyfriend knew about and we had a huge fight. There began my huge ocd cycle. I had a lot of sexual thoughts, feelings like maybe that guy is better and romantic thoughts and stuff which I absolutely hated.
But I slowly navigated from those and the theme kept changing, I’d be obsessing about different things but all had just one target - my relationship. Hurting my bf was the last thing I wanted to do after this incident. So everything that would hurt him, I thought I was doing. I created an image of myself in my head as someone who couldn’t be trusted, who falls in love with someone else while in a relationship, who just has to be with that other guy just because I had a brief crush on him.
So again from the last 6 months I’ve been so badly obsessing about the same thing- wondering if I still had feelings for that guy, fantasising and checking scenarios as how I’d feel with him, intrusive thoughts about that guy when I’m with my man, replacing my man with that guy just to see how that would feel, etc. I know these are so so wrong and I shouldn’t be doing it. I even have started to feel like I wanna leave my boyfriend for that guy cuz a lot of people actually do that. People switch boyfriends (not judging anyone, I’m so sorry) and I feel I should too because I’m feeling a whole lot of this. If I do anything in a day, the other guy is always at the back of my head. ALWAYS. It’s like I’m not able to be happy with my man or be with the guy.
So it feels like maybe I wanna be a good girl and be in this relationship and actually fearful to explore a date or something with that guy. I really don’t wanna be with anyone else other than my boyfriend because he simply is the best.
But my mind never seems to accept that and even when I’m with my boyfriend, that guy is always in my head - especially during intimate moments and I hate it so much.
I’m not at all in contact with that guy and it’s been since 2 years I saw him even

At this point o don’t wanna lead my boyfriend on, we speak of marriage and kids. And I don’t want to lead him on. I don’t want him to feel like I betrayed him. It hurts me so much. It’s excruciatingly painful. But it all feels like beliefs more than thoughts and I cannot for a reason find the right therapists. It’s expensive.

My thoughts don’t feel good anymore and I don’t know what I genuinely feel but it feels like I’m emotionally cheating on my boyfriend cuz I’m involved into thinking about another guy even if I’m not in contact with him.

I feel breaking up is the best choice to do cuz these thoughts feel like urges and feels like I’m okay with these thoughts too about pursuing someone else cuz honestly I don’t know if I want that other guy or not.
Please help me navigate. I beg.

Thanks for reading