Help with birth control

Patient: I started taking birth control (Aviane 21 day) for relief of period cramps almost a month ago.My doctor told me to start taking them the sunday fallowing my next period.At the time, my period was due the week after but I decided to take it that sunday instead of waiting to get my period.I have 4 pills left out of the 21 days and i just started my period now, and still have cramps? should I continue to finish the pills or have my period and take the next pack in 7 days ?I don’t know if I’m having cramps because I skipped it last month?