This is a BIG problem!?

So I really like this guy that is going out with this girl that is sorta my friend. Me and him are like best friends and we talk 24/7 on the phone and IM (even though he never talks to his gf) and we always play truth or dare. Yesterday we were asking stuff like what do you want your wedding to be like, what do you wanna name your kids, that kind of stuff. So his answers were just like mine and I go Omg we have the same future! Lets get married! And I was like obv kidding and hes like okay and so we just started talking and he goes if I was single would you go out with me? I go uhmm yeahh probably. would you go out with me? Hes like yeah. So we just kept talking and hes so sweet and I really like him but hes going out with my kind of friend. Then he says well since i'm going out with her now, maybe we should just try to act like just friends and I go shouldnt we not put on an act for her? I dont know what to do! Pleaseeeee helpppp! (I'm 13 and he's 14)