All jokes aside, I wouldn't turn to a trainer for direction. Even assuming your trainer has had other clients with similar issues that turned out not to be heart related, that tells you NOTHING about what's going on with you. Any trainer worth what you pay them will tell you the same thing you've been told here. Go to a cardiologist and get a full work up. Bypass your GP if you must, but don't let your lack of faith in GPs to prevent you from getting evaluated. This is an area where you err on the side of caution.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher