New to this board.
I'm 47 and periods have been edging closer to every 21-24 days for the last 3 years. But this morning, I have woken to the next one 17 days after the last!
Given the last one was for 6 days that means only a 11 day break. 
Is this normal? Should I go to the GP?
I also want to add that I had horrific anxiety for the week leading up to the last one. I've been getting that on and off for the last 5 years, but this was on a whole other scale. Glad to say as soon as my period arrived it vanished and I haven't had it this time.