First of all: Lots of HA people ask this, among other things
but this is one of those "You could be a redneck" type jokes ONLY it is called "You could be a hypo if _____"
By this I mean your query is such a common refrain around here.
what would I take from a comment like that ^^^^^? I would say, "Okay worrying how to trust a doctor's word pretty much means my thinking is disordered. I have a thinking issue."
Sure there are rubes for docs and some docs make mistakes...actually all docs do from time to time. BUT only hypos would ask "How do I trust a doctor?" The general public accepts that doctors are here to help. When asked questions or are presented with a patient with x, y or z symptoms, they WANT to fix the issue. They don't want to make mistakes. They generally are good, moral people who are good at their jobs. Plus they are careful because they don't want to get sued.
So 1. remind yourself that 'regular' people generally accept a doctor is here to do the job right. If you are continually obsessing the opposite, then you need to recognize your thinking is the one that is incorrect and is TRULY part of the disorder that needs to be addressed.
2. AND looking practically: ask yourself if aren't going to believe the doctor, then why bother wasting your time and money and the doctor's time?