My best friend since Pre K just came on to me and I'm straight.

So my best friend who is a football player were walking around by a forest and he brought up that there were a lot of ticks and that it was called a coon tick, he kept saying it over and over to me but i didn't respond because i thought it was one of his stupid jokes. But he got a little serious and started asking "no?" I said that i saw the joke coming like what it really sounds like. He still kept asking like he was just trying to make sure it was definite. A little while later we see a community pool and he brings up that we should go nightswimming. I bring up that it is locked and our friends dad has the key so we cant but he just say we can get a ladder and sneak in. I tell him to bring it up to our friend first. Later he keeps asking to hang out all of next week since he gets out of school. It all makes sense though, he always make jokes about pretending to be gay but i always thought they were just jokes. And one time we went to an LMFAO concert with him and our girlfriends but when all the people on stage wore only thongs with a stuffed animal heads on the dick area like elephants with long trunks or giraffes he had a raging hard on. I just have been friends with him all my life and its weird that it turned out the way it did. What do i do? And how do it without losing a good friend?