IDK what i have? Heart Pain, Irregular Heartbeat.. HELP?

Earlier this week on sunday i was in the car with my boyfriend and i had a severe chest pain. it felt liek a squeezing but that was it, no shortness of breath or anything. it lasted for about an hour then just stopped. i felt fine. Monday in my computer class it happened aagain but worse. so i went to my school nurse and she gave me tums thinkin it was heartburn, it wasnt, so she checked my heartbeat and noticed it was irregular.
i went to the doctor then to the hospital and had a bunch of tests done. so far nothing. they thought it was diabetes but that came back negative.
i was just wondering what are some possible diseases i could have?
im just kkinda nervous and i dont like waitin for the doctor to call.
please help;
im female, 16 and slightly overweight
if that you needed to know.

I have these!! They are panic attacks. When it happens to me, I get rapid heartbeat, chest pains, the shakes, and feel nauseated, and just downright awful like you are going to die. I also went to the doc and got all checked out. Finally came to the conclusion it was a panic disorder. There is medication that only has to be taken during time of need. Glad I found it!!!
hope this helps

Are you possibly having anxiety attacks? How about Esophageal Reflux? These both have the same kind of symptoms that you have described...

Well, you don't say how much overweight, what is your stress condition, etc. A doctor should have given you a stress test along with EKG, if these didn't show anything, some further tests unless you've seen a good cardiologist.

As stated further down, an esophageal test, your stomach. This nerve is along the same area and does create the same type of pain so...? then there are several other things it could be but, why speculate here, your doctor should be able to give you the advice you need.