My urinalysis also showed high urobilinogen (4mg/dl) and was positive (++) for bilirubin. what might cause this?

Lots of things: Think first whether any medication you might be taking is causing cholestatic jaundice, or whether you might have smoldering viral hepatitis, might be drinking a lot, or might really need to get more exercise -- the latter's a factor in genetically predisposed individuals who get non-alcoholic steatohepatitis. Especially if this is new, do get worked up.