What Causes Brown Spotting And Irregular Periods?

Hi, I was on the pill injection for ten years, so didnt have proper periods, just a lot of brown spotting etc. I was sterilised last April. In September I started having periods again. This month's period started with the smelly brown discharge for five days, then a red blood proper period for three or four days, which seems quite smelly also, compared to normal. I also have had a lot of pain in my left ovary for a long time. Any ideas?