What Causes Bleeding After Periods?

Hi, may I answer your health queries right now ? Please type your query here...hi, I'm so worried right now. I have a period mid december but then had light bleeding from jan 6th and felt nauseus and had pains in my stomach. I put it down to an early period and when it stopped a week later thought no more of it. Tonight I went to the toilet and noticed blood on the tissue now I am so worried what could be wrong with me?