Hello, My Son Is Having Stomach Issues. He Said He

Hello, my son is having stomach issues. He said he has sharp pains in his lower abdomen and has had diarrhea every time he uses the restroom (about once or twice a day). It seems to me though that the only time he feels this way is in the morning after breakfast right before he has to go to school. We tried cutting out dairy to see if it was a lactose allergy, and it seemed to help, but then has started again. He seems fine on the weekends too, but I'm not sure. This has been going on for a couple months, on and off again, and my gut is telling me that maybe he's being bullied at school and is causing nervousness or anxiety, but maybe something else is going on health related. Could you possibly give me some tips and advise on this? Maybe even some things to look for?

Thank you!
Lindsay Harless