I have been in my period for two days. Is it possible that there could be a connection with the Concerta?

It is unlikely that Concerta would have an impact on your menstrual cycle. If you have continued taking your contraceptive pill as usual, there should be no effect on its effectiveness. It is normal for there to be occasional irregularities in your menstrual cycle without any specific reason. Just continue taking your pills regularly to maintain contraception. If you experience ongoing irregularities or other abnormal symptoms, it would be advisable to consult your doctor for further evaluation.