chest pain

I have been having major chest pain the past few days. Sometimes really bad. I went to see my 3rd cardiologist last week. He told me its not your heart. I have heard that until I'm sick. I am 25 years old, I've had every heart test including a nuclear stress test last August. He told me he could do a heart cathrization but at 25 years old the amount of radiation from the test could cause some long term effects.  He also told me that the test will probably be normal because of my nuclear stress test was normal. What Should I DO?