First time post, trouble breathing

So for the past couple months I have been noticing a shortness of breath when physical. I am fine when not active but doing common chores can leave me feeling light headed, very hot, excessive sweat, dizzy, headaches and tight feeling chest. It really hits me when I stop to rest though and some times it's hard to know I've overwhelmed until then. I have had two different chest xrays, lots of bloodwork, ecg, and a pulmonary test. Doctors say they can't see anything of concern yet I still feel like I'm struggling to get enough air. So I'm here looking for anything that could help me point the doc in a better direction.