My 14 Year Old Son Took A Dose Of Antibiotic

My 14 year old son took a dose of antibiotic last night, and today had very little to eat and did 3.5 hours of strenuous exercise. This evening he developed severe stomach pain and upon eating, he developed nausea and vomited twice. He is resting now, but has chills and chest pain. I suspect that the antibiotic which after checking is in the penicillin family (he is allergic to augmentin) probably upset his stomach and then not eating all day and exercising caused his blood sugar to drop and increased acid in his stomach caused minor gas and the vomiting....another factor/scenario is that he has picked up a stomach virus from a team mate who he last saw Thursday evening. Thoughts?