HELP!! period twice this month?!

Okay so I had my period two weeks ago, and then started another period again this week. I'm on day 5 of this second period which is so weird. My cycle is very regular and I have never had this happen before. I had unprotected sex January 2, and I was ovulating but I've had 3 periods since then so has this happened to anyone else and if so what should I do? Should I be worried?