Hi and *hugs*. Sometimes our body can be strange and do the weirdest things. Sorry yours is being that way right now.
My periods are quite regular also, but have had a few months that just throw me off. It's frustrating. I too have had months where I have all sorts of IPS (imaginary pregnancy symptoms) and then AF shows. My most recent is that AF showed a couple of days early. Ugh! (Which threw off my days and I have another month to wait before I can continue fertility treatments because the clinic is closed in July.)
I hope that your journey here is a short one.