Becoming a toxic partner

I’ll keep this as short as possible. Lately I have been seeing a huge pattern within my romantic relationships and how they affect my day-to-day life. In the past, (around 18) I dated a 23 year old who had much more experience than I did (obviously) and it was just something I had to learn to get over. Aside from that, he was a big liar. At first I thought i was just being the anxious, delusional girlfriend when in reality he was indeed cheating/keeping things from me. The way I found out was through the whole reassurance-seeking thing I’d do which I had no idea was tied to OCD. I’d ask him things like “so you never had a relationship with your best friend?” In which he replied no at the time but then months later when I’d have the urge to ask again and he would say “yes I thought I told you”. Situations like this sparked a habit for me in which I had to keep asking my partner things because the answer could be different each time. Couple years down the line in my current relationship, I find myself doing the same things; asking questions about the past because they might give me an answer that’ll tell me that I was right all along/give me a reason to act the way I’m acting. This relationship that I’m in is the healthiest I’ve ever had, leaving me thinking that I’m just this immature, untrusting, pathetic girlfriend that is difficult to please. I keep asking him these inappropriate questions like if he ever did these certain things with his ex partners and then getting upset when he answers. He’s been telling me lately that he doesn’t like to think about his ex partners and wishes that I don’t make him remember those things. My issue is that it just goes right over my head and I continue to do it. A part of me trusts and loves him but another part is just constantly searching for a reason that he isn’t “the one”. I’m 24 now and am ashamed to be acting like this. Can anyone relate?