Im 12 Days Late For My Period, I Have Brown

Im 12 days late for my period, i have brown spotting severe back pain and abdominal crampimg, nausea, and have went to the bathroom and had blood clots twice but no actual bleeding. I went to the e.r. And all test came back negative so they gave me nausea meds and told me to go to a family doctor for more tests. What should i do? Is it normal?