the other day i nearly fainted , blacked out vision, sweating, felt cold but body was heating up. went to the doctor after i came home i pooped green . and after that i have very little to no appetite. feel very weak . and I m 21 years old, weigh about 187 pounds and am 6.2. i feel very tired all the time now. and i don t know what the issue could be? please help i got blood tested, ekg, and a heart ultra sound and everything was normal. because I ve been having pains under my heart, or around that area of the chest , and if i do something like take a quick sprint from one point of my house to another (which would be like 5 car lengths , not much) i feel my heart beating so strong, followed by a pain. and I ve always been a very active person. so please help me figure out what my problem could be?