Is my friend gay?

I met this guy in college and he says that he is staight. The thing is he can be very prissy. He gets his eyebrows done, he doesn't like to get sweaty and he just has a lot of feminine qualities. Whenever people meet him they automatically think that he is a . He even asked me if I thought he was and I said yes. He was very offended because he says he is not gay. He even use to live with a guy who was openly gay. I consider him a good friend and I would still be his friend regardless, but this is getting on my nerves and I want to know. He and I have never been more than friends and never will be. I just want to know. Should I ask him to tell me the truth or leave it alone?