Sense of Smell that no one else smells but I do

Jackie
Yesterday, I kept smelling a sweet smell on random people but the people in the same room as me didn't smell it. My friends say that I'm probably pregnant and go take a test. Others say that I could be smelling diabetic ketones. I took a test and it said negative. I took another one this morning and it said negative. 
What could it be that I'm smelling something that no one else could smell but yet the tests say negative?