can't stop thinking about it

So my boyfriend and I have been together for 4 years now , minus one little break in between for about 6 months . During that time I did my best to move on because I felt like I would never get him back . I started to talk to other guys and hang out ... (I never did anything sexual with them ... just hung out) well this one guy I met was pretty great and we hung out and talked nearly every single day ... I didn't let things go farther because I wasn't over my ex and didn't think it was fair and didn't want to use him as a rebound . This was about a year ago . I haven't really thought of him since my boyfriend and I got back together 6 months ago . Last night I got a request on instagram and a text message from the guy that I was hanging out with during the break ... I didn't respond and I rejected his request to add me on Instagram , and I blocked him for the sake of my boyfriend ( not at his request, I'm just a very faithful person and I wouldn't like it if my boyfriend was talking to a previous potential girlfriend) but all last night and today I've been thinking about how things could have been between him and I . I love my boyfriend to pieces and I would never choose the other guy over him ... I just can't help but think about him and the fun times we had and what it would have been like if we ended up together . Idk what to do ... I hope this passes soon.