Nitroglycerin?

I've experienced severe anxiety and panic attacks since 1998. I'm 49 year old female and was given nitro for pain in my chest. I rarely take it but last night and today I've taken a total of 3. They seem to help.

I have done all the test/stress test for heart problems, but Dr's say all is fine. I've been dealing with heart palpitations since 2003, which has totally made my anxiety attacks more frequent and more terrifying. I'm at my wits end.

I've been on antidepressants, beta blockers, zanax, etc and nothing helps. My Mom and Dad both died from heart disease at an early age. My Dad was 45 and my Mom was 54 when she had a stroke. She died at 57.

I'm constantly worried. I've got 4 other brothers and sisters and I'm the only one that is dealing with panic attacks, heart pain and anxiety. I'm so scared of dying but I'm so tired of living in complete fear.

My question is why would the Dr's give me nitro pills if I have no problems with my heart? Please help?