What Causes An Early Period With Stomach Cramps?

I have a pregnancy question. My husband and I tried last month to concieve a baby. My period came just a day early, but only lasted about 2 days, which is not normal for me. I took a pregnancy test right before my period came and it came out negative, and then I took one 2 days after my period stopped and, it also, came out negative. I'm having some cramping in my abdomen and lower back. Is there a chance I could still be pregnant??