...my mom thinks that my 9-year old yellow lab might have ovarian cancer. she is obviously not a young dog anymore, and she doesnt get to run very much. we have a very small yard and live in the middle of a park with alot of other dogs, so she cant be outside alot by herself. she is overweight, but she is on diet control food. she is starting to trip alot, and she has thrown up a few times within december and january. she isn't spayed. can anyone give me any symptoms at all? could it be that she just isnt getting enough exercise?
thanks in advance.

I would jump to just reg old age, or heart worms, or infection before I would even think of cancer, or even ovarian to be specific.

Take the dog to the vet.