hi there, grandmas' usually have usefull information and she may be correct in her own way but as you have got yourself checked and your belly button seems to be in place we should look for any other probable cause of the pain,.It would be good to get a urine and stool exam done along with an ultrasound
of the abdomen to try and find the cause of the pain Usually one of these tests will be able to give a clue to the pain. In the meanwhile you can tke an anti-spasmodic and plenty of water. Hope you feel fine soon. Take care.