Difference between emotionally cheating and ocd?

Hi, this is my first time posting anything so sorry if I accidentally trigger someone. I've been with my boyfriend for almost 6 months, and we've had a lot of ups and downs but good times too. I love him very much, but lately it's been harder to enjoy the relationship because I feel like I emotionally cheated. There was this guy in high-school that I grew close too over the course of a year, and quickly developed feelings for him. Fast forward, during our last month of high-school I started developing feelings towards my now boyfriend, and it was great. But, over the course of us dating whenever something bad happens I think "the guy I liked in high-school wouldn't say or do that" and it bothers me a lot. I ended up blocking him and I told my boyfriend about my lingering feelings towards him, and after a couple months I unblocked him to apologize and wished him a marry Christmas (which I told my partner about and he was good with it). But, one night when I was on Instagram I saw his story and it was pictures of him and I felt anxious and flushed to the point where my heart started beating and my thoughts felt intense. After that, I blocked him again and told my partner that I wasn't ready and ultimately decided to not talk to him or have a friendship with him anymore. Throughout our relationship, I just kept thinking and questioning whether I liked him or not and other various thoughts. It's so confusing, I love my partner. What should I do?