hi burnsyboy
are you getting stressed out about it before you take your BP?, are you taking your BP at different times of the day?
When I test my BP at home (first thing in the morning) its always fine ie around 70 over 115-120, but whenever I go to the Dr I always get nervous / anxious that it will be high...and thats *exactly* what happens!!!
I know its easy for me to say, but try to relax, dont think too much about it and then try taking it.
good luck!