Is Late Or Missed Period A Sign Of Pregnancy Even With Pregnancy Test Negative?

My girlfriend has hormonal imbalance that was causing her to have periods that were spaced out. She was on the pill until October to help regulate her period. We had sex about a week into November and she did have her period until some light bleeding which she said is normal for her occurred in late December early January. She had a period that lasted a week in early to mid February and took a pregnancy test at home just after that which was negative. We used a condom and I don t believe it broke, but I have been freaking out ever since that missed or simply late period. She is very sure that she isnt pregnant especially since she hasn t had any of the classic symptoms, but I can t seem to let myself be that certain yet. I want to know if she is right and she isn t pregnant and unjust being paranoid, or if there is still a chance she is pregnant. Is she pregnant?