Yes. Yes, it is. It's a sign that neither relationship has a real future.

Idk, aren't you in a relationship now? What is your crush even offering?

These people exist and a lot of us have them. It's just chemistry. I mean...it's with your partner, too but with a lot more work in it so decide wise. Either you don't want the relationship you have or want but then remember: some people make us react harder then others and it's not a universal sign. It's just a neurophysiological reaction on molecules. Not that exciting as it feels sometimes. I know very well that it wouldn't work out with the person i had these reactions for so i let it go.

If you're already regretting trying to work it out then it's broken. End it and move on.