IBS, Crohn's, ulcerative colitis, celiac disease, and
food causing gas can be the other possibilities.
Hip pain can be due to osteoarthritis
, tendonitis, muscle pull and strain, sports hernia or hidden/occult hernia of oblique aponeurosis, or Obturator or ilioinguinal nerve entrapment.
You would need all or any of the following for diagnosis: Clinical examination by an orthopedic specialist, X-rays, blood tests, MRI or ultrasonnography.