constant stomach pain

My son is 3 yrs old and he is been complaning about stomach pain, every time I take him to the Dr. is always the same answer, is just a stomache flu well  is been 6 months and my son still complaning, and know is not only he's stomache but also he's teeth please can anybody help me?
Dr. recently  order some blode test and stool example and, everything cameback  normal . but what about the stomache and teeth pain.

[kooldy]

if your son is teething it can comenly cause tooth and stomch pains i would know i have two nephews and a baby brother who which i went through teething with all three of them