My period is very different. It is brown, very light, and causes l soreness?

Most people will have an odd period at some time or the other the darker blood is just blood that has aged so it is a bit older the fresher blood tends to be brighter red. The soreness is a bit unusual but if it is not to bad I would just wait and see. It might be your period is being affected by a l infection if it gets any more painful or you notice an unusual discharge or a nasty smell then get medical advice