Hi. I have four guinea pigs that I love very much.

2 of the pigs live together separately (both boys). The other two guinea pigs I have is one female and a neutered boy together.

I got the female and neutered boy about 4 years ago almost. The boy is visibly older...he has pea eye and he is chubby...his breathing is a bit heavy but I took him to the vet for a checkup about a month ago and they said he was healthy (I changed bedding and it's cleared up).

But now...his female buddy is having problems. She has always looked very young, and she still does. She's at least 4 years old, since she was about 1 years old when we got her (we think). Since we've gotten her, she's always been chubby, about 3.5 pounds. I brought her to the vet a month ago too and the vet told me she has an ovarian cyst. She had also lost 5% of her body weight since the last time I brought her in. Now she's noticably lost more weight, I can easily feel her hip and spine. She's also had a lot of energy too...when she was younger she used to squeal for her meals and climb on the cage and she's been doing that a lot now, and she hasn't done that for a while until her weight loss. pets question and answers,www.5d2d.com

I'm getting worried about her. I'm taking her to the vet on Wednesday. Any ideas on what this might be?

A guinea pig losing weight is a very bad thing!
Guinea pigs are prey animals. this means they will not show signs of illness till it is to late.
One of my guinea pigs is 7 years old and has ovarian cysts as well.

My advice, discuss all your issues to a vet. Its what they are there for.
Good luck