Why I Am Having Chest Pains ?

Why Am I Having Chest Pains? What's Causing Them?I'm 18 years old, and have been having chest pains for the
past three years. It's not in one particular place, I have it mostly on the left side, and the middle, and sometimes radiates to the right side. Everytime I go to the doctor they say everythings fine which includes: the heart, lungs, breathing, etc. I always have trouble breathing when the chest pain occurs. The pain has gradually gotten worse, both in the amount of occurences, and the intensity on a scale of 1 to 10 ten being the most severe I would rate the pain as an 8 or 9. When I was around 13 or 14 years old a speacialst had sent me to a pediatric cardiologist to see if I could take some medicine. While there I had an EKG done, and the results said that one side of the heart is slower than the other and I think that's my right side, and that a normal heartbeat beats in the following order chamber 1, 2, 3, and 4. Finally, in August of 2006 when I was 17 years old I had experienced all the signs of a heart attack my dad had said that I was having one, it didn't seem like it. Help.