Friends w/ benefits, a few questions?

I happen to be in love with my best friend. He rejected me saying he didn't want a relationship right now for various reasons. We are still best friends but it was awful and hurt like hell. I know he likes me though, I can tell. We don't have a normal friendship. But, I have another guy friend who I met in Uni. We aren't great friends, haven't been friends long but decided that we should become friends with benefits. Is this sleazy of me? I have no emotional attachment to the FWB, aside from being friends. Should I tell my Best Friend about this? And am I embarking on a really bad journey? More importantly, would this hurt my chances of having something more with my Best Friend? I was hurt really bad when my best friend didn't want something more right now. I understand why he doesn't but I'm still hurt. I've never done anything like this before and would like some feedback and opinions on the situation. Nothing has happened with the FWB yet as it was just decided.