2.) Are you stressed? Stress can cause that kind of pain.
Always make sure when you go to a doctor that you let them know how bad the pain is on a scale of 1-10. When I was having chest pains my doctor made me get an EKG to make sure nothing was wrong with my heart.
Also pressure applied to the chest may cause some sorts of chest pains, aswell as some trouble with the stomach. Anxiety may also cause chest pains. But if the doctor didn't find anything abnormal in the heart film, or didn't notice anything while listening to your heart. I doubt it's anything to worry about, it might be just anxiety.
However if they didn't make a heart film, then yeah.. I guess you should ask them to have one. You're still really young which makes it extremly rare for you to have heart trouble.. but sure it's not impossible but not just really likely.