What Causes Cramps And Spotting After Menstruation?

Hi, I am 19 years old and have recently started suppressing my mestruation with monophasic birth control pills. This is the third month I'm doing it but this morning I started getting cramps and spotting, which throughout the day turned into a light period that stops every so often. I am very scared and worried and am wondering if I should continue taking my last week of pills or if I should stop and let my period happen. Please help me. Thank you for your time