How to get over a straight crush?

Hi, I'm a 18 y o gay male and still in the closet. I've never told anyone about my sexuality and I think I won't untill I'll go to the Uni, there I'll start again without lies. I'm an introverted person, for this reason I have not so many friends, but I'm not lonely, I have a group of friends, and we meet us every weekend, they are really nice, but there's a problem; in that group there's a guy, who I have a crush on. He's so beautiful and he's a good person, I like his body and his personality, I know that having a crush is not exactly loving someone, but he's always on my mind. The situation is not easy, I cannot tell him what I feel also because I think he's straight; once he asked me for advice about a girl he wanted to flirt with. This situation started from September and it keeps going on, I tried to convince myself I don't like him anymore, but everytime I see him I fall in love. I know I should keep the distance, but he's in my only group of friends. What should I do?