Well I guess i'll put my two cents in on this one. I have tons of "straight" friends but over time they have become curious. Most people know at least one person that wasnt gay but after that "drunken night" or at least thats what they blame it on, now are or at least they are open to it. This is something that sticks in your mind especially when you have strong feelings for someone that is straight and wish they were gay. You never really know until you ask them out. I mean you dont go and ask them "Hey are you still straight today" so over time, especially if you have a close relationship its most likely going to happen. Just tell him you are still straight, nothing has changed but do it in a good way. You dont want to lose