Period came three days earlier and was ending and starting again for four times

I am 21, turning 22 in October. My period is usually good with timing. I would be a day early or a day late, here lately it would be a few day early or a few days late. I always had horrible menstrual cramps, to the point where I double over and about to tear up. It would usually be heavy for about two or three days then lighten up and end after about 6 days. Well I started my period last week  on the 6th and that is three days earlier than it was supposed to be. It finally stopped on the 11. It was fine then came back for a day on the 13. Then came back for another day on 16, then another today on the 19th. I don't take birth control because when I took the pill on the first day, I end up in the hospital on two bags of IV. I never had this problem before. Last month it stopped in the middle and started again but still ended on track so why am I going through this now? I know I have a little cyst on one of my ovaries but I had that for a while and this never happen before. Can someone tell me what is going on with me and why?