You most likely have a sinus infection that blocks the path to your olfactories. I used to lose my smell when i had chronic sinus problems. In fact, it made me desperate enough to try the technique which became ultimately successful in curing all of my sinus problems forever. Solutions:
Go to ENT, get antibiotics, see if that works
or, get a Neilmed Sinus Rinse at the drugstore, which has a better chance of working
or, go to my journal and try a Flip Turn Sinus Flush. It's risky, because you have to bend over in a shower to get the saline where it has to go, but it's highly effective. I think the greater risk is losing your sense of smell, which can be severely depressing.
http://www.medhelp.org/user_journals/show/2322
Oh, and don't use any anti-cold pills with zinc, that can also mess up your sense of smell.