Mating Hamsters?

Question
I have owned dwarf hamsters for almost 5 years now. I have always housed different sex pairs and have never had them mate. Recently I have seen my hamsters on top of each other a lot. My hamsters look the same until you turn them over, so I picked up the one on top and it was the girl! I was wondering if this is normal behavior for breeding hamsters. If she is indeed pregnant (she has always been fat) SHe should give birth the week of my wedding. I dont know how to tell. I looked at the pregnant campbells pic from one of your previous posts and she always looks like that so its hard to tell... HELP!!

Answer
As I stated in my profile I am not an expert on hamsters at all so I refer people to Heather, another expert in here.
The post you are thinking of must be one of hers.

http://www.allexperts.com/ep/2005-34607/Gerbils-Hamsters/Heather.htm

Contact her and ask her this question.
Girls in the same cages will often exhibit this kind of behavior if they are in heat.
Cows are commonly seen doing this.