I've had this issue before. Being interested in someone you don't think you should pursue due to a relationship, etc. Getting creepy vibes. In my case, I went on a work trip, and this person said they were handing me beer, but really it was spiked with whiskey. I like drinking, but the dishonesty rubbed me the wrong way. Your situation is that you're kind of crushing on this person, which I totally get as well, I actually wanted to have sex with this person, but I was in a committed relationship and wanted them to respect that.
What I ended up doing was having a direct talk with them, saying I think you're interested in me, but I'm in a committed monogamous relationship and don't want to pursue this further. Nothing happened from then on.
In your case, I would talk to HR. Prepare for there to be a fallout, because men can get real sour about this stuff, but what you're describing sounds like predatory sexual harassment; whether you are interested in this person or not, you are being made uncomfortable at work by this person's presence, and his behavior sounds extremely inappropriate and deliberate.
TL;DR - talk to HR