What Can Cause Irregular Periods?

over the past 7 months i have started taking birth control then i stopped taking the regular pill and took a lower dosage for some time then stopped that all together. For two months i have not had my period and this past friday i had a period for less than one day which started and stopped is this normal when coming off of birth control. About two months ago i had unprotected sex for 5 minutes and he did not ejaculate.