What Causes A Heightened Sense Of Smell?

A few days ago, my sense of smell became extremely heightened to the point of obnoxious. There were no specific changes in my life on that day, and I know I am not pregnant. It has gradually gotten worse over the last couple days. Not only do I smell every smell around me in a very strong way, but a lot of the smells almost have a "burning" smell to them. Any ideas?