To what end Joanna? My opinion is that if he was interested in you, he'd have the ring on your finger. He obviously loves you as his best friend...you'll take a risk to lose that friendship if you burden him with that truth.
Think seriously of all what could come of it....and the repercussions and possible regrets afterward. Unless you can say it in a way without it being a burden of admission, giving your best to them for a happy future, etc. Who's to say it'll work out....
I understand your plight, truly.....you will risk, but if it makes your heart lighter....maybe he already knows how you feel....and you'll be at peace with the admission. I just hope once he knows he doesn't tell his girlfriend.
q