Katey, for Christ's sake, you're already best friends and it sounds to me like you love each other, too! Seems to me as if its this big elephant in the corner that you both notice, but no one is saying anything out loud about it because you're both afraid.
Love is all about taking risks--I say you have to take the risk and talk to him! It may be the best decision that will ever make in your life.
Let us know what happens! Good luck.