Does he just want to get into my pants?! >.<?

Pull away form this guy, you are his "reserve" girl; whenever something is going wrong with whoever he is with at the time, or he is feeling lonely, he will come to you because he knows you will always be there like a faithful pet. One of my friends dealt with a guy like this, and she got her heart broken several times by him & he never changed. That's why he doesn't want to be seen around with you, because he doesn't want people to ask "isn't (your name) your girlfriend?" He wants you to be behind the scenes so its always on the down-low and none of his girlfriends get jealous or suspicious about you.