What Causes Delayed Periods Along With Pre Menstrual Symptoms?

Im 19 and married. We dont have protected sex. The first day of my last period was December 7th. Its usually regular. Im 3days late. A few days before my expected period I had some pms symptoms, Bloated, moody, and constipation. Im still feeling bloated and i have diarrhea. Ive also gotten a few small pinch feelings in my abdomen. I took a pregnancy test but it was negative. Could i be pregnant?