I am sorry you are feeling this worry atm. I know how this feels...and it is so difficult not to catastrophize.
Remember that this is part of your HA. Thinking the worst case scenario...when in fact, it's not the reality...only a manifestation of the health anxiety.
Try to keep in mind how many times in the past you have been scared of something that turned out to be nothing.
This time will very likely be the same!
Make the appointment, and keep your positive mantras on a loop in your head!
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"Worrying does not empty tomorrow of its troubles...it empties today of its strength."
Corrie Ten Boom
Panic Syndrome recovery due to CBT