So that was the wake up call I needed.
On further investigation, 3cm is OK at 22 weeks if there are no other presenting symptoms, and there aren't. Blood pressure is perfect, no glucose issues, no infection etc The only issue is my platelets. I am border line.
Dr K said that the issue was that on the ultrasound (on top of belly - is that a sonogram?) measured short - 2.7 but that measurement is not reliable. I will have the cervix checked often to see if it goes below 3. It isn't the measurement but the amount of change (i.e shortening) as you all knew, my dear clever folks.
I am not to work more than 35 - 40 hours a week. To put that in to context, I hit 36 hours by Wednesday. No flying.
So, I will cut down on work. I will eat consciously and for the benefit of the melons. I will rest up as much as possible and I am wearing my belly belt to reduce the pressure down there. I will approach this as I did my weight loss - follow the rules and stop trying to control everything!!!