please help

Alright so this week I have been bleeding brown blood and I keep passing brown blood clots. I know it's old blood, but the thing is , I'm not supposed to have my period until next week. I'm cramping really bad and I've tried googling it and all that comes up is implantation bleeding. All the posts say that you're not supposed to clot and bleed constantly so that's not it. I do have sex, but I'm on birth control and I've been on it for a year.  This birth control has given me trouble before. Last month I started my period two weeks early and I was passing blood clots. I'm just really confused if this has something to do with my birth control, if I started my period early, or If it really is implantation bleeding.