What Causes Diarrhea After Eating And Delayed Periods?

I have had diarrhea everytime I eat, for 4 days now. No cramping, just nausea. Certain smells make the nausea worse. My period is dues in about 7 days. I took a pregnancy test (HPT), it came back negative. This would be my second child. I didn't have diarrhea with the first. Since I have been pregnant before, I remember what my body felt like, I feel it now. Is it possible that I just took the test too soon?