Urine How often do guinea pigs pee?

I'm not 100% sure whats wrong with pecan but besides her back legs not working and a couple of lumps I'm not sure if shes able to pee which is obviously an immediate issue. She peed at about 2:30 at the vet but the vet had to squeeze a little to get her to go. Its been almost 4 hours and she has still not gone on her own. I'm wondering if this is normal or if she should have gone by now. Her left side is swollen. Is that the side with her bladder? Does anyone know how to make a guinea pig pee? I don't know where to squeeze and I don't want to hurt her.
Shes been pooping but I don't think its a normal amount. She has been eating. Not sure about drinking.
We think this could be caused by an infection so she started baytril and metacam. Otherwise we are thinking mammary tumors because of where the lumps are but I don't know if mammary tumors would have anything to do with her back legs or not being able to pee. Could it be neurological?