Please help, urgent!

So I got my period the 11-16 & it was very light. There was no cramping at all. Then on the 23 I got the usual cramping and I started my period. This has never happened to me before, should I be worried? Am I just spotting? I also haven't had sex in 4 months (I always wear protection) and I got my period every singe month so I really doubt I'm pregnant. But has this happened to anyone? Should I be worried? Please comment anything!