possible pregnancy in adopted guinea pig

Question
I adopted a year old guinea pig from a national chain pet store 3 weeks ago.  Samantha had been turned back in to the store as one of the owners had developed "allergies" so I was told.  She is so sweet and loving so I adopted her with the understanding that she was not pregnant.  I questioned the store as she was very fat.  We are now very concerned that she is indeed pregnant and is too old to safely give birth.  She has prominent nipples and just looks pregnant.  She is adorable, loving, very very sweet.  We have all fallen in love with her.  Please advise.  Thank you very much.

Answer
try not to panic too much, if she is pear shape then it is quite likely, in all liklihood she will be fine in birth, but it might be a good idea to have a vet check her over and definatley a good idea to find a guinea pig friendly vetiner clinic so when she goes into labour you can take her there IF any complications seem to be arising.

all of that aside good luck and congrads