What Causes Stomachache Followed By Watery Eyes And Runny Nose?

my son is 4.5 years old. today the school called to take him back because he is having stomach pain and crying. he is a strong kid and this was alarming for us. so we took him back home, he felt relieved to see us. he said there was no pain now in the stomach, but we saw his right eye was watering and right side nostril discharging and the right side of under lip was painful. no fever. we thought this unusual so we took him to Doctor, he couldn t find stomach ache and eye or nose discharge related and suggested Brufen and an antihistamine syrup and ask us to monitor the kid. back home he was sort of OK. His lip pain was gone, stomach pain didn t happen again and eye discharge was better. but the nose kept discharging time to time like in flu. we checked the nasal mucus and it continues to be Brown. warm brown but not red like blood. He had 105 fever two weeks back, bad throat and was treated with Ceclor 250mg. So, is this some after-reaction to the antibiotic? Any Ideas what is going on? Thanks