My Voice Has Been Coming And Going For Over A

my voice has been coming and going for over a month. It started a month and a half ago when I was at work, in a dirty environment. By the time I left that night I was already hoarse. an by the weekend I was in the immediate car getting predisone shot and predisone for 12 days talking above a whisper. It got better but it still comes and goes and I get tired if I walk around too long and I have chest pains that come and go. ENT said my throat looked fine. Pulmologilist said my longs looked good and the blood test he did showed no pulomonary embolism. Any suggestions?