Negative pregnancy but spotting

Patient: Hi, my period is regular and come around the same time every month. My last period ended on the 26/09/14 and my next on was due on the 24/10/14 but didn’t show up. 2 days later I started to get brown discharge mostly when I’m wiped. It appeared on and off. A week being late I took a home pregnancy test which was negative. Another week went by and still getting this brown discharge on and off. So I decided to go to the doctor to get a blood test which was a negative. I don’t really have any other symptoms because sometimes I think most of them are in my head like my back pains and pains where my overies are and bloating. If it’s not pregnancy what is it?

Symptoms: Late period, spotting, back pain, bloating