What Causes Prolonged Menstruation With Vaginal Spotting?

Hi my name is LIza King I have irregular periods but I always start them either somewhere at the end of the month or by the tenth or 15th but this month it was weird it felt like I was starting my period on the first very light pink period it was like that the first days then I felt a pain on my right side for a day I was like that and now it went away but now I'm on the eleventh day and I'm still on what it seems to be my period but there is cloting and very little blood and normaly my periods are heavy and last 6 days what's going on ?