Questions about female rat

Okay I was looking at oreo, she is supposed to be about 4 or 5 wks but she looks extreamly fat. Could she be pregnant because she was housed with her male rats before I got her? She is much bigger tha ev-ey stomach wise. Heres some pics:
http://img103.imageshack.us/img103/5135/1012581si1.jpg
http://img165.imageshack.us/img165/4552/1012582uw4.jpg
I'm most likely just being paranoid though.

It is possible that she is pregnant if she was kept with male rats prior to you bringing her home. Especially, if she came out of a pet shop. It is said that rats ARE sexually mature at a minimum of 5 weeks, I personally, I have seen rats that are no older than 6 weeks pregnant and give birth. It is really not good for them, and usually they dont make good mothers that young.

That being said, how is she eating, does she eat alot?

Is her poop runny or not very solid at all?

Usually they appear quite pear shaped then some with larger litters get very big and round in the belly. Most will start building massive nests out of their substrate within 24 hours of giving birth. Near the end of their pregnancy you can often catch them sleeping full out on their backs (thought rats that are overly warm and not preggie will also do this). Hope she's not preggers at such a young age. If she housed with other females, she could also just be hogging most of the food...some are like that the piggie little boogerheads.

she has been eating alot and laying much. still playing some with ev-ey but mostly eating and sleeping. lol But she has gotten much bigger just in the past week thats what caught my attention. It up came so quick. I didn't know if she was preggo or just a growth spirt (sp?)