How to get over one particular obsession?

I'm struggling really hard with relationship obsessions. Do I really love my partner? How can I know? Am I really just faking it? That kind of thing. It's making my life and relationship a lot harder than they need to be. I could use a few helpful coping mechanisms, trying to move away from less helpful ones like chasing reassurance.

Looking for inspiration

So, I know my capacity to get fixated on things. And it's normally something that's relatively remote but, my latest issue is really getting to me and I was wondering if people have any advice. I'm avoiding getting too into specifics, as I don't want this to get reassurance-y but, in essence.. I came to the realisation recently that people who I'd been "friends" (feels like the wrong term now) when I was younger were not very nice people, and normalized a lot of very unpleasant behaviour towards other members of the group. They really normalized it, sold themselves as figures of authority, as older and more responsible and grown-up than others, and looking back, they acted horribly. And coming to this realisation, that I'd been manipulated into just accepting their behaviour has just... broken me. My OCD has latched onto it and I can't stop feeling irreversibly tainted by it. I've talked to others about it, and they've reassured me, told me it's not a big deal and that I hold myself to too high a standard, but none of that sticks. I feel better for a bit, then think 'Maybe when you told them you were skewing it to make yourself look better' or 'Did you leave out a crucial detail'. I keep ruminating over and over, trying to remember exactly how everything played out, trying to figure out if I fed into the behaviour, if I did something bad myself (because y'know, I feel like I was accepting of it at the time, so what does it say about my own values?). I know I need to stop doing all this if I want to improve, but then some part of me keeps saying 'So, you're just going to let yourself off the hook then?' Normally, I can rationalize my own fears to some degree, assure myself something won't happen, but the realness of the situation, and the fact I only came to understand the reality of it because the thought had been bothering me means it feels so much more all-encompassing. I know confessing in itself is a compulsion, but I keep feeling that if I'm not I'm somehow concealing what I 'really am' from others around me, and any positive interactions are me deceiving them in some way. I feel like I can't enjoy anything in life right now, and a good part of me feels I should not enjoy it ever again. If anybody has any advice on it, I'm all ears. Or even hearing if you relate to these feelings, I might appreciate the solidarity at least.