Are phantom smells symptoms of a brain tumor?

Approximately a year ago I began experiencing strange smells, almost like a chemical burning, that I quickly determined was not actually in my environment, as no one else smelled it.  The episodes were intermittant and happened in numerous places: car, home, outside, etc.  I thought maybe it was scent overload - I have mulitple scented oil plug-ins in my home - that had affected my sense of smell.  Then last summer I had a mild cold and stuffy nose.  While home I decided to seal my granite with Impregnator 511, which is very strong stuff.  A day later my stuffy nose was gone, but I'd lost my sense of smell  completely.  It took about six months for it to return, and still not fully.  Alcohol often has an ammonia aftertaste and things just do not taste or smell the same as they used to.  I assumed the inpregnator had damaged my nose, as I was all stuffy when I used it and couldnt really sense how strong it was.  (Bottle says to use in a well ventilated area with a mask - which I obviously read after the fact).  Still, I continue to have these odd episodes of smelling something burning.  Then, I was watching NIP/TUCK, of all shows, and the doctors mentioned that phantom smells are often indicative of brain tumors.  Now I am extremely worried.  Does anyone have any suggestions or comments?  I would greatly appreicate it.