I had second menstruation 12 days after another, now i don't know if my cycle has changed or i'm late?

Menstrual cycles : Menstrual cycles differ in every woman. The length of the cycle can vary from 21-35 days and may involve anything from spotting to heavy bleeding. Various life stressors can change the cycle from month to month. Pregnancy, new meds, illness, travel, weight gain/loss, excessive exercise, STD's, endometriosis, and Polyps can cause changes in periods. Talk to your Dr if the problem lasts more than 6m