What Causes Abnormal Vaginal Bleeding While On Birth Control Pills?

Hi, may I answer your health queries right now ? Please type your query here...I had a little bleeding after my peroid this time which was about a week ago. Iam on a pill birth control. This morning i woke up and the bleeding is much worse, and theres some blood clots in it, i also feel very weak. I also feel like everytime i just get done peeing i have to pee again, but only a tiny bit comes out this morning its been blood. Whats going on with me.