Got her regular period 4/12 -4/15. was sexually active during the time. only used birth control pill. got another period 4/22-4/26. what caused this?

Depends : You are on a Progesterone only pill, norethindrone. If you don't take this pill at the same time every day, you will get breakthrough bleeding. Remember, on the pill no one gets a "period". Withdrawal bleeding occurs during placebo days of the 21/7 or 24/4 day type combination pills. On your type of pill bleeding is unpredictable and hopefully will go away over time! there is no "need to bleed".