I NEED HELP WITH MY GAY FRIEND! HELP!?

My friend and I are close. Both males, 12 (me) and 13 (him) and in 7th Grade. We tell secrets, have fun, etc. But usually we don't hang out. So I was pretty excited on Thursday when he invited me and my other friend to his house. We went to his pool, and at first the day was normal. But later on, not so much. There was a storm coming, so my other friend went inside along with my friend (who owns the house)'s parents. We stayed outside though. We were laying on his hammock, which was funny because we rocked it and fell off at certain points, but he put his legs over mine and had me keep my legs down and kind of... spread, I guess? But whenever his parents would come outside, he ran to a separate chair until they left. Then we went inside and played Twister. Yeah, him and me (I already felt weird) played Twister while our other friend would spin. Then we played dead later, because apparently that's cool (... and fun?). He pretended to like rape me. I'm not saying it was really awkward, because he was joking and funny, but, whatever. Then he straightened my hair because I said I had a bad hair day. Okay. It was fun + funny. The next day, we went to his house again for the pool, just us two. Again, at first it was alright, but then he told me to go undrwater and for about an hour we just did things like sex positions and he put my hand on his crotch and his on mine. I don't know if for him it was like it was for me, because for me it was joking, even though it was awkward and felt good, but... then he put his hand down my pants. Awkward -- definitely. But it felt good, and I liked it. Now, I didn't mention this, but for a while, like a year or two, I've been contemplating whether I was bi or not. I know for sure I am recently, but I'm not sure about my friend. He's had only girlfriends, but he's sending me these signs! I have a girlfriend, in fact, we started going out that night, after I left, but I have strong feelings for this guy. But what I like, just not as much, I guess? was that when we dried off inside his house alone, he waited, finger in mouth, as I put my shirt on. When I asked why he had his finger in his mouth, he said because he had nothing else to have in his mouth. I passed it off with a laugh but when I went to leave, he told me to wait and pointed at his crotch. I, again, passed it as a joke, but he was serious. He was disappointed, I could tell. My problem? Age. We're 12! (He's 13, whatever.) I haven't told him I'm bi, because even though I trust him and I know he loves the gays and everything too, I just think it would ruin the friendship. Also, what should I tell my girlfriend? We JUST started going out, and although it's pathetic to break up with her after like two days or so, I don't want to lie to her. I love her, but I definitely love this guy, too. If I go over there alone again, should I ask if he's bi and explain that I am and have feelings or no? He's just as close with my girlfriend as i am (even before we started to go out), so that's I guess the only thing I'm worried about with telling HIM. My girlfriend, on the other hand... Maybe I can tell her I want to take a break to sort things out and see what it's like with my friend (without anyone but us knowing, of course). Well, this is my life. Drama. In freaking middle school. Wow. Answer, please! And sorry about the length.