2 periods a month

Molly

I started BC and I have used it before, I also have used the brand I am currently using but I've noticed since November I've started getting my periods more frequently. I get them literally every 2 weeks now. I assume it's a side effect from BC and not sure if it's normal. Should I be concerned? Has anyone else had these problems? BTW I've used BC on and off since I was 17. I am now 22 and this is the first time my menstrual cycle has been off.