Same here. First period since was a few days late, otherwise fine. Second one was a week late, with period pain each day for 7 days from the day it was meant to arrive (when normally I only have period pain for one day) then my period finally arrived and I had the worst pain I've ever experienced, which kept going even after it stopped - all over the course of 11 days in total.
This is exactly what I experienced! After I got the second Pfizer dose.
I had the vaccine appointment in the morning and in the night I woke up with fever. I had high fever, headaches etc for two days.
My period arrived ten days late (very unusual for me).
I had a different kind of pain, it felt like uterus cramps, for a full week and normally I have some pain and cramping on the right side on the first day.
It started with spotting, then a very heavy period for one week, and lighter bleeding for a further three days.
Also felt very tired.
I did a bit of research online and read that the general guidance is that the vaccines do not impact the female cycle.
But then I read that the form with the questions doesn't even ask specific questions about periods, anyone filling out the form would have had to make a separate comment on it.
I feel that they should have put more emphasis on this.
but so far my period is not as painful and this is my second since my second covid jab. It also seems to be back to normal flow with no clotting. 
