Why is it the only think I think about?????????? How can I convince myself it isn’t true when it feels so real??????

When an intrusive thought comes I can’t just say “that’s not true” and just move on. I always feel like I have to disprove the thought and be able to say it with confidence but the problem is that the ocd doesn’t allow me to feel and say it with confidence so I get stuck for hours or even days. How can I stop feeling like I need to do this?

It feels like I used to get so many intrusive thoughts in the beginning but now it’s less it’s only thoughts like what if I’m a p what if I’m a p what if I’m lying to myself what if I’m in dentist truly in all this and it was all fake like I’m an imposter, now it’s just feelings and noticing :/ and I hate he feelings that come with it I’m really scared I am one I feel so alone :( I’m taking therapy but my therapist is not specialized in ocd and I don’t think she understands and I don’t want to bring it up bc I brought up a fear that what if I turn into my stepdad and she said “are you attracted to children?” And I said no but it was just an irrational thought that came after I started realizing the trauma that happened to me as a kid, and idk I’m scared to Start with a therapists here bc what if all this just makes it worse and it turns out I am what I fear all along.? :(

I know he’s not cheating on me. He’d never do that and, as hard as I try to tell myself “he’s proven already that he’s not” and show myself all the signs of commitment and dedication, I still have that fear. It’s eating at me and ruining my relationship. How do you guys get over this? If my brain were true he’d have been cheating on me for months in ways that aren’t even possible. It doesn’t make sense if I think about it logically but it seems like when I do, I create in my head more ways for it to be logically true. What is your advice? How can I stop self sabotaging?