If cheating is kissing/sex then what is this?

This is my 2nd relationship. First was 4 years now this one is going on 4 years. I've noticed when I'm out and about I have a roving eye. Friends consider me a flirt too. I've only ever had 2 boyfriends and I have NEVER cheated but I always have these little crushes on cute guys. It never goes beyond saying hi, chatting, telling them I have a bf, and flirting. What am I doing?? Am I just needing attention? There's a cute guy at the gym that has been smiling at me for 3 years and now I want to come say hi and I'm all excited about that and find myself nervous with butterflies etc...do I just like the attention or am I trying to replace my boyfriend subconsiously?