I Take The Ortho-tricycles Lo Regularly. I Caught A Stomach

I take the ortho-tricycles lo regularly. I caught a stomach virus that had been going around work. I had both vomiting and diarrhea. This was on and off for awhile. I had unprotected sex and he did finish inside. I happened to be ovulating during this time. I took plan b the next day. Shortly after taking it I threw up again. About 2 weeks later I had light spotting for 3 days. I took a hpt that came back negative 2 days after. I went to the doctor who did a urine test a week after the spotting that came back negative. It has been 3 weeks since I spotted. Is pregnancy a possibility?