Dream guy

I finally met a guy who is just wonderful - we get on really well, been on a few dates, and I've not laughed so hard with someone like that for so long. He is kind, caring, knows what's going on in the world, and is introducing himself to new things because they're important interests to me. We had our first kiss a few weeks ago... and have gone exclusive. 
Cue me crashing at a mate's barely a week later... and sleeping with the mate. Wracked with guilt doesn't even begin to cover it. 

During the day I dream about the first guy. In the night I long for the second. And I don't know what to do.