I'm sixteen years old and I have had upper abdominal pain and chest pain for the last three or more weeks. I am very scared.

Relax but evaluate. At your age this is more likely to be irritation of your swallowing tube than anything serious. It can/does hurt & many people immediately thing it is heart related.Avoid acidic foods/carbonated drinks & caffeine. Don't eat or drink within an hour of laying down.Go in and be evaluated.