The pain in the abdomen is most probably due to adhesions formed after surgery.
If the adhesions are mild,all the investigations will come normal.
If they are severe,you will present with vomiting
So,i prefer you to go for Laparoscopy(key hole procedure) and see inside the abdomen.If there are adhesions,they can be separated at same time.
It can happen after any surgery in the abdomen.
So,please do not worry
Consult a Surgical Gastroenterologist and proceed.
Wish you good health