Hello and welcome to the forum where you willl get loads of help and support from the wonderful ladies on here who will completely understand and have experienced what you are going through.
With regard to the white coat syndrome, you are not alone, I am terrible, as soon as a medical person comes near me my bp goes through the roof and I have to keep explaining the reason why. Once I am at home doing my own bp readings they are totally fine. You would be surprised how many people actually have the same problem so you are not alone my dear.
Just take a deep breath and deal with each stage one at a time, so for now it is preparing yourself for the op on Wednesday and then deal with the results after that, try not to second guess the outcome as that is only going to make your stress and anxiety worse.
Come on here whenever you want or need to and we will get you through this, there is always someone on here who will be abe to support you.
Sending you hugs