Where is the pain centralized? Does it come and go? One bit of advice I have for you is to log every time you feel the pain, what level of pain it is (1-10), type of pain (ache, stabbing, burning, etc), what time of day you had it, what activities you did before the pain, what you ate or drank. Then go back to the doctor with about a month's worth of notes and see if that helps them determine what could be causing it.
The problem with obscure abdominal pain is it could be a symptom of a whole myriad of ailements... IBS, menstrual cramps, pinched nerve, anxiety, acid reflux, allergies, gallbladder... and about 1000 other potential causes.