Does metformin delay your cycle?

I started taking Metformin around two weeks ago. My AF was due 6 days ago. I've been having the worst cramps for more than a week now and feel like I have a sore cervix. I know for sure I'm not pregnant (not even gonna bother with a test) because we last BD'd a few days before I started taking metformin and I'm pretty sure it wasn't in my fertile window.

I've had a very delayed cycle once before (a few months ago) and my cycle has always been 31-35 days.. isn't Metformin supposed to regulate your cycle instead?