Last few days I have had trouble breathing, as if I have to force myself to do it. Also I am really tired and get this episodes of extreme lightheadedness. Sometimes when i have trouble breathing I get an urge of anxiety sort of feeling in chest. I had blood tests and ecgs done and thyroid tests as well, all came back perfect. Last week I was suffering from heart fluttering 2-3 times a day. Doctors say they are not concerned cause I am 20 and tests are fine, but symptoms persist. What should I do?