Hello, could I be pregnant? I've been on Yasmin birth control for a couple of months, I'm 18. But I'm now 4 days late for my period... Is this suppose to happen, I thought the pill was supposed to also regulate your period. I used to have,very irregular periods, sometimes a 4 month gap and then 5, and then 3 months again. It always use to change. Me and my boyfriend don't use any other type of back-up method, only the pill. I always take it on time, I haven't missed one. The past few days I've had cramping and discharge, which usually happens before my periods. What could this mean?