rocksinmybed

What is the difference between allergy and multiple chemical sensitivity? I have had sinus headaches and congestion since childhood. The problem was worse when I was a child because my father smoked. I have always reacted to smoke, exhaust fumes, formaldehyde on new fabrics, dust, as well as cold, humid weather and weather changes. About 25 years ago I was exposed to a large amount of insecticide when I foolishly acted as my own exterminator to rid my new residence of fleas. Ever since, I react to strong odors such as perfumes and highly scented flowers by developing a headache. I live in an apartment that is partially underground. We have had some problems with mildew. I am also not the best housekeeper and collect a lot of books and papers. My congestion has been a lot worse since I moved here, especially in the winter when the windows are closed. I have just been diagnosed with severe sleep apnea and must use a CPAP machine. Therefore, I must get myself cleared up in order to use the machine. My ENT has prescribed Rhinocort nasal spray and I intend to give it a good trial. He really didn't discuss the cause of my condition except that my turbinates swell and if the spray doesn't work they may have to be surgically reduced. He doesn't think I need to see an allergist. I don't think he would even entertain the idea of multiple chemical sensitivities.
Should I see an allergist anyway? Should I try to find an environmental medicine specialist? Thanks for any help anyone can give me.