Turns out at some point I had had a subendocardial heart attack and have heart failure as a result. Taken several years to get a diagnosis. It's frightening really. It would be at any age for sure but at 31 it's even more frightening. Thanks for the support of this forum over the years and whomever it was on this forum who advised I get a CPET, had I not done that I never would have been diagnosed so thanks a lot.