My son has has abdominal pains for over 2 years, doctors says growing pains, but I'm not sure. He is 6'2 165lbs and very athletic.

Time to visit another doctor.

If the doctors have said there's nothing wrong, and you don't believe them, then see another doctor until you get the answers you're looking for.

There's really no way for anyone online to give a diagnosis.

He is 16. He could still be growing. If you are not satisfied with what the doctor says, take him to another doctor.