Terribly confused

Okay, so I have a serious relationship problem. My mind and my heart are stuck between two guys, and I want some neutral, outside opinions of the situation. So here it is, nutshell version:

I'm dating a guy who I believe I love(call him Aa), but I have lingering feelings over an old friend. The old friend (call him Bb) is a person whom I am almost certain had feelings for me, but after months of trying to give him his chance to make a move, he never did. So I moved on, and started dating my current boyfriend.

Now, here's the long version

Aa is a wonderful guy. We met through a mutual friend, and we hit it off and became friends rather fast. I'm his first, and (naturally), he's very attached to me as a result. I love his family, they're wonderful people, and they have grown to become a part of my life. There are, of course, those moments in our relationship when I wonder why the hell we're together (particularly when he does something that makes me especially mad :P ... I also know this kind of sentiment is common in longer relationships), but he has so many redeeming qualities that I can't help but love him.

As for Bb, we also met through a mutual friend (a different one, though). When I met him, I was finally getting ready to date again after a long hiatus from the relationship world. I'm always troubled by the fact that I seem to have to be the one to make the first move, and so I decided that my next guy would have to make the move on me. For months, we hung out and did all of the boyfriendly/ girlfriendly things... went to dinners, watched movies and cuddled, went on weekend trips, etc.

Progressively, despite feeling that he had an interest in me, I gave up. I got tired of going to all of the trouble for this guy, and looked in other places. That's when I found Aa.

We started seeing each other and I, (for the most part), cut myself off from Bb, refraining from doing anything that may stimulate old emotions for him. I would later find out that the mutual friend who had introduced Bb and I had been interested in me. To this day, I feel the reason Bb didn't do anything or make a move is because of our mutual friend (not wanting to hurt him and all).

Anyway, Bb and I have started hanging out a little bit again, and old emotions have resurfaced. I still care for him in more ways than you would for your typical flash-in-the-pants, but I'm held back by the fact that I love Aa. This was precisely what I didn't want to have happen. I was a cheater once in the past, and I recognize this pattern of behavior in myself. I know deep down that there's no place for both of them in my heart, and I will have to make a choice at some point. I can't help but feel whichever I choice I make, I will break a heart.

The problem at its root is that I can't imagine my life without Bb being in it somewhere. He's such a wonderful person and I care for him so deeply. But I think now both of us are at a point where we're so afraid to even discuss it, for the risk of causing a rift. It could be that he actually never had any interest in me, and this feeling I have is just something I'm imagining. However, during the saga of Bb's and my awkward, almost-relationship phase, my friends informed me that he did indeed care about me deeply as well.

My question is, what would you do? What would your choice be? Stay with the new guy, or run back to the old flame, and why? Would you talk to the old flame and find out where he stands, or just forget about it?

This especially drives me crazy because I vowed to myself after I cheated my first (and only time) that I would never consider doing something like that again.I don't want to live up to the 'once a cheater, always a cheater' saying. But, when I think of Bb, I want to be with him. I don't even think about Aa.

So please, someone, shed some light and offer some guidance for me on this one. Also, feel free to ask questions. I may have left some stuff out and not noticed. Thanks a million, and please try not to judge me too harshly for this one.