I find I get more hot and bothered and achey doing stuff. Some of it is my fibromyalgia and some of it is expectation I think. I know whenever I do stuff I'm thinking " I hope this doesn't give me chest pain, raise my blood pressure etc etc ." And I hyperventilate because I'm worrying so that gives me more pains etc. I figure that if I can go on my exercise bike for half an hr and not keel over I'm ok, and the fact it goes away when I stop thinking about it.
I think your GP is thinking that referring you for further tests isn't only unnecessary but will just feed into your health anxiety, and really unless you have an angiogram which is dangerous and can cause serious heart issues/ death you won't ever be sure ( and I don't think even then) as you could have stress test today and be ok bit still have heart attack tomorrow.
Being stressed is hard on the body and makes everything much more physically draining so try and relax and just breathe. Remember that anyone who hasn't been active for a while starts up again they would feel achey, tense, unfit , breathless etc. x