Projected feelings?

I'm going to tell my coworker that he reminds me of a person I used to have sex with. Things are starting to feel awkward, I find myself glancing over towards him and too often I find him holding my gaze... there's no way he doesn't feel some kind of strain. I feel like I'm hiding secrets.
I'm really nervous honestly, I don't know where to begin. I'm not even sure of his sexuality, but even then..

Has anyone else experienced this, feeling attracted to someone because they resemble someone else you are or have been attracted to?