Pregnant or tumor?

Question
I have a female rabbit who is about 4 1/2 years old now, not spayed.  I have another male rabbit living next to her and they are separated by wire.  The other day when I came back from college, I was going to pick up my female rabbit when I noticed her belly was abnormally large.  I don't know if she's pregnant or if it's some type of disease.  No one who cared for her when I was gone knows how she would be pregnant since they don't remember the two rabbits being together.  I don't think she's just gaining weight either because you can basically feel every single bone in her body other than her large belly.  I also noticed her urine was spotted with blood.  I'm clueless to what's going on.  Is she pregnant?  Does she have a tumor?  What do you think is happening here?

Answer
She may be bloated. It doesn't sound like it is pregnancy, especially if she is showing the signs you mentioned. Rabbits can easily get some pretty bad digestive problems. I would highly advise getting her to a good rabbit vet asap. She might have a tumour, but it could also be any number of other problems causing the symptoms. A lot of problems in rabbits cause the same basic symptoms.