Hi Blueangelz,
This sounds fairly complicated. I am not even sure how to approach this with the information given. The short of it is you need a doctor. This could be anything from cardiac to psycholigical/anxiety driven -- this cannot be decided over the internet. When you do see your doctor and if it is a new doctor, make sure you bring all your medical records including the MRI itself, not just a report.
I hope you find an answer soon and wish I could help more, don't feel comfortable saying much with the information given.
Good luck