I want to have with my straight friend?

But here's the problem. Everyone thinks I'm straight, and I'd like to keep it that way. He has a girlfriend, and while I don't currently have one he and everyone else knows I have dated quite a few women (I'm , so please don't tell me I was leading them on). Anyway, thinking about him is driving me crazy, I seriously want to get with him. How do I go about testing the waters to see if he is open to that without 'blowing my cover'? We live in a conservative area, there are 3000 kids in our school and no one I know of who is openly gay. It pretty much stays on the down low here, how do I subtly test his uality?