Why Are My Menses Not Stopping?

i normally have regular menstrual cycles that last for 7 days. This month my cycle started on the 22nd & hasn't stopped. it's now 14 days. it's not heavy very light. some days i think it's going to stop cos it's extremely light but in the afternoon some blood comes out. what could be the problem. i'm 30 & not on any contraceptives.