I so relate to you! I went away last weekend and came back 2.2 lbs heaver! I am also a big calorie counter but knew that there was no way I could accurately estimate what I was taking in last weekend. I cope with those days by getting back on the wagon - making sure I do some cardio, drinking lottttts of water, and trying to limit my carb intake (since carbs can hold onto more water). It took me almost all week to get back to where I was, but now I'll start recording my measurements again!
I think as long as you don't use one bad eating weekend as a reason to just give up and go crazy with it (I mean, I indulged, but not ridiculously so), you'll be okay. I hope that helps! *hugs*
I lost 15 lbs in the months leading up to my wedding, and gained it all back in the aftermath! Time to get back to that better weight!