I have been taking this pill for about 5 months. The first 3 months my period was the same as it was before I was on the pill, except the cramps were much lighter. It lasted about 5 days and the blood was bright red. It was lighter when it first started and the last day. The only difference is this would happen twice a month (every 2 weeks). However, the past 2 months my period has been very light. It's only lasted 3 days and only been brown. Also, it only happens once a month during the week between packs. I only have 21 pills per pack. Why could this be? I'm becoming very concerned