Feeling attracted to another person while in a relationship

I’ve been with my current boyfriend for over a year and a half now and he’s just perfect.This is the first serious relationship I’ve ever been in, and so far it’s been amazing: we both like each other’s friends and families, we always make the other one laugh and we also have a very good sex life. I’m completely in love with him (and so is he), but a couple of weeks ago this guy from our town (whom I already knew before) hit on me while on a party, and even though I told him a few times that I have a boyfriend he kept telling jokes and being kinda flirty (he was also a bit drunk though, and so was everyone).

The problem is, my boyfriend was there as well, and he got really angry with him (not with me, because he saw me explaining that I am in a relationship and overall keeping my distances), so I had to split them up in front of everyone.

Now, I don’t question being in love with my boyfriend — because I am. But now I’ve noticed that I’m thinking about this other guy quite a lot. And by that I mean that if he asked me out or something I would most definitely say no, but I wouldn’t mind seeing him again while on a night out.

Has this ever happened to you? What do you think about this situation?