How to tell if a mouse is pregnant?

Question

I bought a pair of female mice almost about a week ago. One of them was a little bigger then the other when I bought them. Now she is either fat or pregnant but I can't tell. Are there any ways to tell if she is pregnant or just fat. She is beating up on the other mouse, which is definitly a female. When I feel the underside of her belly there is an obvious bump and her hip area looks fairly large. However, I'm not exactly sure because the upper half of her body is sort of large too. Just wondering if there's anything I should look for, and if I should seperate the mice. I might seperate them anyway because I believe by the squeaking noises I heard they are fighting with one another

Any help would be great!

Thanks!

Answer 1

 Hi my name is Becky                                                                                                                   I bought two female mice from a pet shop a couple of weeks ago and got them checked and their both definitely girls.

But latley one has gotten huge she looks like she looks like a pear which is what i heard their spous to look like when their pregnant she is getting bigger and bigger all the time and she is also nesting alot it been past 5 weeks but this is her first litter any advice is welcome?

Is she Pregnant or should i be worried?