What the hell is going on?

Okay. First, I’m almost 4 months PP. Second, had my tubes tied. I’ve had two period since the baby and my third period was due 6 days ago and I still haven’t had it. So no period, negative pregnancy tests. But my moods are off the wall, lower back hurts, I’m crampy, can’t sleep, no energy, no motivation. Can anyone give me some insight on what the hell is going on with me? I know stress can hinder your period and yes I’ve had stress going on but I’ve never had stress stunt my period for a full six days I’m usually only like 2-3 days late. Anyone have any insight???????????