I'm officially crazy!

I've posted before about feeling pregnant and wondering if I was. Well my period is supposed to start tomorrow and today I took a pregnancy test which was negative. I'm fairly confident that this means that I'm not pregnant and I'm just trying to wait out my period. But damn I could have sworn that I was! I'm starting to feel crazy! My boobs are still bigger and my back hurts, as well as having random bouts of nausea (I never ever get PMS symptoms, either). Could I possibly be having a thyroid problem?