Abnormal periods, loss of appetite, negative preg test! HELP!!!!?

I came off the pill in March. I didn't have a period for a while, I came on on the 21st May. Period was brown discharge, and was lots of clots. This episode finished on the 28th May. I then had spotting for a week starting on the 3rd June, this finished on the 10th. I now have a similar episode to the 'period' I had on the 21st May. Also for the last 3 months my appetite has drastically changed, I can no longer keep certain foods down, the taste of most things has changed. Foods I used to love I can no longer stand, and foods I used to hate I like. I done a pregnancy test today, it was negative. Doctors have done blood tests to check if I am anaemic, this came back normal. I'm going out of my mind. Any suggestions of what this could be. I've went from a size 12 to a size 6 within 3months.