Suggest Treatment For Diarrhea And Abdominal Pain

My son was dealing with diarrhea and stomach pain 2 wks ago. He would feel better in the middle of the day, but the nights and mornings he felt the worst. He did not have a fever, but felt weak. Then last week he felt better and stools returned to normal. This week he is getting stomach aches again and mostly at night and morning and is feeling weak again. So we went from one week being bad, then next week better and this week feeling bad again and slight diarrhea. Still no fever, but he did throw up once and says he feels like he will get sick. The only common thing is that both times this started after he had an ice cream cone. We can t figure out what is going on. Any ideas? Doctors tell us to give it a week, but offer no solutions.