Break up?

I’ve been with my boyfriend for about 1.5 years now and we’re both currently home for the summer so it’s practically a long distance relationship right now. Now I’ve done long distance before and it’s never been like this. For example; we bicker a lot, have gotten into a few serious arguments, and even when we went to LA and had a vacation together things felt off on my end. I only say on my end because he told me that he didn’t feel the same way. Something else that’s been happening recently is that I’ve been fantasizing about other men and it makes me feel so guilty. Especially because one of the guys I fantasize about is a guy I used to hookup with before I met my boyfriend. I’ve never acted on anything nor do I plan on it, but I often find myself daydreaming about a taller guy who doesn’t have as much family drama as my current boyfriend. I keep trying to brush the fantasies away, but it’s getting kind of hard, especially without my boyfriend around. I thought maybe the fantasies were because my boyfriend is transitioning FTM???? And maybe my fantasies will go away once he’s fully transitioned? I need help. Are fantasies about other men normal? Or am I an awful girlfriend??