I'm kind of in the same situation... I liked this girl A LOT as a friend but all the time I was hoping that we could be more. Then one day at a party we flirted a lot and even kissed a bit, but the next day it all seemed kind of awkward.
After that we weren't seeing each other as much as before, but we finally got to talk it through and agreed to just being friends. We were both at terms with that, and hung out a lot more again...
Then this weekend things went too far when we were drunk and we slept together. The next day we didn't talk about it, and I feared that we had just ruined our friendship forever. Luckily we've talked about it now and agreed that we went to far because of the alcohol and agreed to continue just being friends. But the way I felt the two days in between is the worst I have ever felt, because I almost lost her as a friend once, and I thought that now I had done it again...
So my advice is that if you really appreciate her as a friend, then let it stay at just that...