Well for about four years, I've ALWAYS had trouble with physical activites because I run out of breath so easily. If I start running I have to slow down almost to a walk before I reach even 100 metres. One of my friends at school believes I have asthma, I'm not too sure though, wouldn't doctors have identified it within me? Or can it come on over a short period of time? I get a horrible burning sensation in my throat and I really struggle to breath, sometimes I can't speak or sing because it gets so bad. Anyone have any ideas about what might be the problem? It's really annoying.