I've had the same problems lately. Actually it has been going on for a long time and recently much worse. My doc thought it might be a thyroid problem and tested for it but that was negative. Not checked yet for possible polyps. I've gained a lot of weight and I think that may be at the root of my problem because it is at least partly related - for me- to breath control. When I warm up properly including arm stretches it is easier to reach the higher notes but still not possible to reach the E and F I used to reach. Last week I began doing crunches with an 'ab roller' and there is some definite improvement with my breath support but still no E or sustained D's for that matter. Thanks for all the information. I take an antihistimine daily. I also use a C pap machine at night for sleep apnea. I think my vocal problems began about the time I started using this so I wonder if that doesn't have something to do with it also.