help plz

linda

ive been feeling sick like from 4 months ago. i used to train hard everyday. now i feel so drained out.. whenever i get up i feel unbalanced and light headed i also feel fast heartbeat and i feel like i cant breathe freely .. i really cant be normal. it really sucks. what tests shall i do to find out whats going on thyriod or iron ? any thoughts ive been thro alot of drs . still cant find whats wrong