Anything is possible, but don't get discouraged yet. Go see your doctor and get tested. that's the only way to be sure.
That being said I have been in long term relationships where my partner knew of my condition and we engaged in unprotected sex multiple times without her ever testing positive. If you two used protection the chance is very unlikely.
So again, anything is possible and the only way to know for sure is to go to your doctor and get tested.