Search Results: having sex often

So recently I became friends with this guy and we grew closer this summer as we started to work together more as time went by we found our self getting closer. I love having him around and i do consider him my guy best friend. But before then he never mentioned having a girlfriend and now he has one and apparently they've been dating on and off for a year and he would always complain to me bout her. He would call me everyday and if I didn't text him back he would get upset but remained playful about it. Or he would talk to me and be like "oh my girl's calling, but I'm not gone answer it" Now all of a sudden he's all about his girlfriend and went from calling everyday to barely texting me back or when he's with her I can't talk to him at all or when we're talking he has to hang up in my face or cut our conversation short. I didn't really mind him having a girlfriend because after all we are friends but I loved the attention he was giving me and now I find myself a bit jealous. At one point he would get jealous when other guys tried to talk to me or we discuss me dating or the guys I dated. I never would've imagined I would feel a type of way about him because at first he was nothing more than a buddy. A lot of people mistake us for a couple and he never denied it. He knows better than to ask me for sex because we've talked about the topic in general but he also mentions how often him and his girlfriend have sex and I don't show the discomfort I feel I just act like my goofy self and joke about it. He also compares me to his girlfriend a lot yet he doesn't want me to meet her and if I'm around and she calls i have to be quite. Or he doesn't want her to know we hang out. He's never tried to make any moves on me and we're "just friends" so I don't see why he has to hide our friendship from her. But I'm clueless as to what his intentions are. Should I tell him how I feel? Guys what goes through your mind when you do things like this?