Dropping Hcg levels

So on Wednesday I went to the doc to do a blood test. She said I was around 5 weeks but it a little hard to tell as my cycles are irregular. My hcg was at 3100.1 which was really great. On Thursday morning I had brown discharge. I figured it would be okay Later that morning there was more. Today, Saturday I went in for another blood test and my hcg dropped to 1103.

She said to come in on Tuesday morning for another blood test.

Has this happened to anyone else?