What Causes Drained Body Feelings With Breathing Difficulties?

i have a feeling conbtancdt my whole body is so drained. i have a hared time to breath some thimes .i no i dont get all the mike i would like to get but so much money .i dont smoke or drink. i do take walks when i can. but still the same i take one aday vitamen.I"m 49 now and feel very weak.laura