Its a fantasy because you are a male and don't have the right parts to feel it as a woman would.
If you wish to live out your fantasy just be very careful and wear/have him wear protection.
Sometimes you need to hear its a fantasy and leave it as such.
If you are gay thats one thing but if you aren't gay why then why?
If you are thinking you might be gay then you aren't because if you are gay you would know it already.