Hello Lucy, and welcome to Anxiety Zone. My name is Chuck, and I am one of the Global Moderators here on the site.
For those of us with anxiety disorders, one of the worse things we can do is to feed our anxiety through non-supportive measures. For a person with health anxiety, this includes getting on the Internet and "Googling" their symptoms. This is one of the worst things you can do.
In your case Lucy, you got on the scales. So to begin with, stay off the scales. There are probably many reasons why your weight was so different in a four day period. Some of these include that a scale at your doctor's office is going to weigh differently than a home, bathroom scale. In my doctor's office, they weigh me with all my clothes on, and don't even want me to take my shoes off, whereas at home I weigh myself with just my underwear on. At home, I weigh myself in the morning, only, as that is considered the most accurate time of day. Most of my doctor's appointments have been in the afternoon, when a person can easily weight several pounds more. Also, if you are currently having severe anxiety, your body is in a state of "fight/flight", and this will cause your metabolism to be increased, meaning that you will be burning more calories, and can actually lose weight even through your eating habits have not changed. These are just some of the factors.
Lucy, during my last severe episode of anxiety, I lost 13 pounds before my weight stabilized. I have gained all my weight back, plus an additional 10 pounds. I am now on a diet-LOL!
So, I suggest you not only stay off the scales, but do all you can to get help to treat your health anxiety.
The very best to you, Lucy!... Chuck