Pet Store Guinea Pig Pregnancy

Question
Hello, I bought a female Guinea Pig on Sep. 2nd from a pet store. Lately she has been drinking a lot more (a whole bottle some days) and sleeping a lot more (just plops down and rests). She is slightly pear shaped, but she has a long coat so i can't tell that well. She gets easily bothered if the other female enters her personal space. She is also considerably bigger than the other female (they are both females, I double checked to make sure it just wasn't sexual dimorphism and same relative age). It has been 72 days and I am wondering if she sounds pregnant even though it has been slightly longer than the standard gestation period.  Thank you very much

Answer
Hello Chris!
Well sounds like your guinea pig has what I call F.P.S., which stands Fat Pig Syndrome. It sounds mean but I swear its normal. Your guinea pig is probably just a little bit larger than most, like when I got Gypsy (my F.P.S. victim).
Gypsy is significantly larger than her sister and mother (Shadow and Cat-Woman) and I thought she was pregnant, turns out shes just large.
Drinking and eating more is actually just your imagination or normal as guinea pigs actually eat and drink less while pregnant.
One more fact against the preggers theory is that she would have been due earlier this month.
I suggest treating her as normal but if you really are concerned and she beats the odds of all the facts against her, try feeling her tummy and pelvis gently with your index fingers for movement and enlargement.