No Period!?

Sammy • I have the most amazing husband ever an adorable 6 year old and a beautiful baby girl born 7/27/16!
I'm used to my periods being irregular because I have been having them every few months since I was 16 but this year I've had one every month until July. I'm not pregnant (took a test) and now I'm just really worried that it's going back to the way it was ):