The pill and your period

Ive been on sprintec for about 4 almost 5 months now and my periods still arent regulated. The first time i got my period after starting the pill, it lasted 4 days and came towards the end of my pill pack. The second time it lasted 6-7 days and came towards the beginning of the end of the pill pack. These last 2 periods came during the start of the 2nd to last week of my pill pack and lasted until the start of the new pill pack.

I have an appointment next week with my gyno but im wondering how long does it take to get regulated, and what has been your experience on the pill whether it sprintec or another brand?