Bleeding problems

Hey sorry if this isn't the right place ! But I've came off my leveste pill about two/three weeks ago whilst I was at the end of my normal period which was fine , but now I've been bleeding for a week straight and I don't know what this is could someone shed some light ? Im really worried about this and I've had no other symptoms apart from feeling sick when stressed . I'm 17 years old if that makes any difference ?