Hi, im having my period for the second time this month. i am on birth control i don't know if this is a causing factor, can i stop it?

Once a year?: A woman with natural cycles of 28 days (shorter than 1 month) will likely have 1 period per month during the year, but have 2 periods during one month of the year (since she has about 13 cycles a year). Likewise, a woman uses 13 packs of birth control pills a year. Since there are only 12 months in a year, she'll have 2 periods in one of those months, and 1 period in the other 11 months.