What Causes Slight Bleeding And Back Pain After Periods?

Hello Doctor! Every month my period is normally finished but afterward it keep little bleeding for while (more or less 5 days) while i got pain from my lower back! Do you think my bladder may leak? But why keep bleeding after my periods? It is urgent! i have been worrying about that! I am a deaf student! I need to know whether it is a serious condition! I will truly appreciate your feedback! Thank you! Cyberoxy