Let the initial tests continue to put your mind at ease, because if you had anything serious they surely would have caught it.
I had chest pain too, not long ago. I was so afraid I might have a heart attack that I almost went to the ER. I'm still not sure what it was, but I had it almost every day for about a month-- Pain like a dull ache when my breathing increased, like with light exercise, and sometimes it would shoot up my neck or across my collar bone to my shoulder. My dad had something very similar, along with a cough, and the doctor told him it was a viral infection in the bronchial tubes that would just have to work its way out. The fact is that chest pain could be caused by many, many things, and the chances of it being serious are extremely slim. Especially for a young person like you.
My doctor and I were talking about anxiety today, and she assured me that it really can cause actual physical symptoms in a person. One of the most common ones I hear of is chest pain and shortness of breath. Maybe your pain is caused by anxiety, or maybe your anxiety is making it worse. Regardless of the cause, you will get through this. Just take it one day at a time until you feel better. You WILL feel better. :)