Could Prolonged Periods Be Due To Irregular Usage Of Contraceptive Pills?

I ve been taking birth control pills (Dasetta 1/35) since June of last year. Last month I missed 2 pills in the 3rd week of my pack and followed the directions to continue taking the pills for that week, didn t take any of the white pills and start a new pack on Sunday. My period has been going on for 21 days