Smells that aren't there

Since the start of my pregnancy, I've constantly smelled smoke in the house (just in one specific room). No one smokes indoors, so that's impossible.
I used to smoke before my pregnancy (but never inside). Could it be due to quitting smoking, or can hormones make you smell things that aren't actually there?
By the way, the smell bothers me terribly, while I don't have any issues when someone smokes outside...