I have trouble breathing for years. What could it be?

Female, 56, for years have trouble breathing tightness in chest diagnosed as asthma maybe but wonder. This year has been very hard; hurts to breathe, lump in throat feeling, inhaler kind of helps but not much, this comes and goes but occurs several times a day -- often worse after eating, or being active -- tried to take a simple walk yesterday on level ground and had to stop -- get "pins and needles" feeling off and on in fingers, lips and toes -- when I do the breathing test they say it's normal or nothing to worry about -- when I did a stress test on a treadmill I had to stop the faster it got couldn't breathe, nitrate pill stopped it immediately but they said my heart looked good -- it is NOT panic attacks --