What Causes Dizziness And Persistent Pain Under Left Breast And Armpit?

For the past month, I ve had persistent pain under my left breast and in my armpit. It s sharp and I d say on a scale of 1 - 10, it rates an 8 or 9. I suspect that it s a muscle and not mu heart. I had what appeared to be a major heart attack two or three years ago: was standing by farm way out in Central Valley and felt nauseous, got in truck and drove about 3 minutes when it felt like a sledge hammer in the middle of my chest, then pain down arm, into wrist, and then arm went numb and I blacked out for a minute or so (awoke on side of rode; had been going about 80mph - very lucky); because I was way out near little towns with rotten hospitals I drove about 3 hours to my home in the Bay Area. It was another 6 hours before they drew labs to check for enzyme. Didn t show up. (my middle upper back and kneck hurt for a few weeks after; felt like whiplash); also, I was dizzy for approximately 5 weeks prior and after this event I no longer was dizzy. After 3 days I went to Stanford and met with a very respected cardiologist. He sent me for a CT-Scan, and the results indicated that my heart looked great. He was stumped. He explained that maybe they did the labs wrong, or, maybe it was a sever angina attack, which could be fatal. He restricted my activities, and after a bout 3 weeks, I called and said, You either tell me I had a heart attack, or I m done with this. He said he was worried that I was going to fall over dead. I said that there are worse ways to go and went for an eight mile hike, then pushed myself hard again that night. I ve been fine ever since, and my EKG s and labs have looked good. But, now, this pain is persistent, and I m wondering if it s indicative of a heart problem. I have a critically ill child on IV s through the night, and lost three contiguous nights of nursing care for him. The sleep deprivation at 46, and the amount I ve experienced since he was born in 03 could contribute to health issues. I figured I d ask. Probably muscle pain, but wondering if heart issues present themselves in a similar manner. YYYY@YYYY