For ongoing stomach pain, you should see your regular doctor. They will be able to diagnose what is wrong with you. If it requires further diagnosis, they will recommend you go to an endocrinologist.
Gastroenterologist
A gastroenterologist treats stomach pain.
Gastroenterologists - I had one for my ulcer
A GP should do.
dentist, eye doctor, podiatrist, pyschologist.
You should see a dermatologist
It depends. If you want to be a physician (a medical doctor), you should get into medicine. If you want to be a philosopher (a PhD), you should get into liberal arts.
An Orthopedist or Orthopedic Surgeon.
Anyone with two hearts and a TARDIS
A cardiologist.
orthopedic specialist.
You should always talk to your doctor if you have any kind of persistent problem. Internal allergy possibilities are no exception.