Phantosmia is a condition where you sense odors that are not really there. I'm having the same problem, and other possible causes are drugs, head injury, seizure, or brain tumor. I hope you have seen your doctor about this, and if not, please do.
Hi there.
These olfactory phenomenon may be due to symptoms called 'auras' which may precede or come after an episode of migraine or headache. These auras can be in the form of other sensations such as bright lights, floaters, goose bumps, bitter tastes numbness on parts of the body which may signal an impending migraine attack. Another possible but relatively uncommon cause are olfactory seizures which be due to some problems in the frontal lobe of the brain. It is still best to have this known to your doctor and probably be examined thoroughly. Regards and God bless.