struggling with this obsession, need some advice.

just to say, i am not trying to seek reassurance, i just need some advice on how to respond to this correctly. so for the past 6 months, ive been stuck in an ROCD spiral, mainly me doubting my relationship and questioning whether i love my partner and want to be with them, the whole 9 yards. my main struggle with this theme is the lack of feelings i’ve had towards him that follow the thoughts. like id have a thought, i would check the way i felt, feel no love or connection and that was my “proof”. the past few weeks ive actually had quite a lot of breakthroughs and i’ve been great. the other night i was laying with my partner, and i was just thinking about how much i love him. and how much love i felt for him. and then it began literally instantly. switched on me. long story short, i was unfaithful a few years ago, it was strictly online, i was 18 years old, i didn’t end up telling him about it until over a year later…but he knows. i was 18 when i cheated, 19 when i told him and we are 21 now. and i have NOT been able to forgive myself for it, at all. in that moment i was lying there with him, i had an OVERWHELMING feeling that i didn’t deserve him, at all. i’m a horrible person, im a liar, he’s too good for me, i don’t deserve him at all. and what haunts me even more, is when i DID tell him, i told him the vast majority of everything but i sugarcoated some things and lied about some things, told him i forgot a lot of things but i really didn’t, in fear. (i did end up trying to open up about this but he said if there was anything he wanted to know he’d ask, he never did ask and i respected that) now, my ocd is eating this up. i feel like i need to re-confess every single detail and tell him im such a liar and a POS. this has turned me back into a shell, sitting in our room researching and beating myself up. now i also feel like everything i say and do with other people is cheating. i genuinely just feel like im a terrible person, a liar, and that i just need to leave him so he doesn’t have to be with someone as horrible as me. i just need help on how to respond to this bc im genuinely stuck in a spiral and need to climb my way out before i actually re-open this wound with my partner and potentially ruin our 7 year relationship. (i also want to say, please don’t make me feel like shit for being unfaithful, i KNOW it was wrong, and it is something i would NEVER repeat.)