I like my guy friend, but he has a girlfriend, what should I do? PLEASE HELP!?

Okay, so before you call me a home-wrecker and a bitchh, I just want to put out there that I don't want to break them up, I'm glad he's happy and I wish I didn't feel this way. They've been together three years. We've been good friends for over a year now, and we hang out a lot. He's 17, I'm 16 and we're both sopres. Whenever we hang out he hugs me a lot, and he always pays the most attention to me out of all of our friends. His girlfriend is really nice, and cool, but she doesn't joke with him in the same way, I'm used to swearing and making some crude jokes with him, but she doesn't like that. I had a party a while ago, and he couldn't come because of his play, but ended up coming anyway around 11pm, and staying till 4am, and we just talked all night. Then, at our mutual friend's birthday, he stole my book from my bag, and I told him to give it back, saying I would tackle him if he didn't, he told me to bring it, so I did. Then, we played hide and seek, and I was in a small dark room, and he followed me in there to hide. Then we watched a movie and igned ourselves to different characters, reacting like it was really happening to us. In the end, our characters fell in love, and the random blond girl who we made his gf, didn't end up with him like we thought she would (she wasn't there. I'm kind of the only chick in our friend group.) Then he went outside, so I locked the door, and he walked away, so I followed him, and asked, "where are you going?" and he said, "let's take a walk" so we went to the play ground and made up our own constellations and joked around till our friends found us. The next day us and another friend were at our friend's play, and he joked with me all night about how the three of us were on a date, and when the other guy said, "NO WE AREN'T" he said, "Okay, just us." Then today, I got a new bike and asked if he wanted to ride and hang out, and he said he had to baby-sit his sister then, he got out of it for a couple hours just to hang out with me, and he tuned my guitar and I said, "Play something" and he said, "Okay, I'll serenade you" and played me a song by his band. Then he played me Blister in The Sun, which he knows is my favorite song. Then I was talking about how the girl next door and I were "not BFFs" and he said, "Well, you know I'm already that" I just want to know if he likes me and what I should do. I've dated several people since I started liking him, but I always come back to him for some reason.