I've had my period 13 days out of 31 days every other week I'm not on birth control or anything. This started 3 months ago otherwise I have always had a regular period. Please help should I go to the doctor? What could this be? Can this lessen my chances of having kids?

Definitely see a Dr. It could be a hormone issue you are having.

By all means, see a doctor, it could be anything from sudden stress to something more serious, so don't delay and just have it check out.