Always ask yourself: 'What's the point'?. Really, ask yourself what you hope to accomplish with this (or any personal issue). Think carefully about the possible outcome, and if it's worth it.
Alot of times people ask questions or make statements about themselves without really thinking it thru. Then, when the unexpected happens, when they get a reaction they weren't intending, it's pretty devastating. If your friend is totally unspecting that you're gay, it might end the relationship. You have to be prepared for that, and ask yourself if it's really worth it.
Alot of times, people say they want to get stuff 'off their chest'. But, that can be not only very risky, but a little selfish, too. Because you're thinking only of your own needs, not the feelings of the other person involved.
I'm not suggesting that you not share things with your best friend. I mean, that's what best friends are for. But, maybe if it's to 'feel better', you might come up with a better way to do that, privately within yourself, that doesn't risk losing something nice, and messing someone else up, too.