What Causes Irregular Periods With Brown Discharge And Pain In Uterus?

I have had an irregular period for the past 3 1/2 years. At first my period would be extremely heavy and would skip 4 months until my next period for the first two years. Now, I have had this period for over a month. It started off light for two weeks, then began to get regular, and now it goes back and forth from bright red and light to semi-heavy and brown. I have not had cramps but recently I feel small sharp pains right where my internal reproductive system is located, especially in my right ovary. What do you think is happening?