Two week period after skipping sugar pills

Patient: I am 17 and sexually active. I have been using the birth control pill levelen for 4 months. I have skipped having my period 3 out of the 4 times, but now I have got my period while taking the active pill and have had it for 2 weeks. mostly it is brown discharge but it has been almost black red too. Its not very heavy, mostly light and I keep thinking its going to finish but it just doesn’t. Is this anything to do with skipping my period those previous times or should I be worried?