Incapable of recognizing chemistry?

I have this major problem where I'm unable to gauge how much chemistry I have with someone I'm dating. It usually happens that I perceive more chemistry than there actually is, and sometimes it even happens that I perceive chemistry and the other person totally doesn't. This is really bothering me because I feel like I'm basically deluded and can't recognize a good thing when I see it. (I do not go for bad guys or anything like that... just guys who end up saying they're not my type or don't "feel it"). Any advice?