Fellow health anxiety sufferer here. Your post is a great example of what makes health anxiety so tricky– being a person means having a body, and having a body means lots of things, some strange, some tiny, happen to it. We all get these sensations all the time, and often is up to us to know when they require medical attention. So the odds are your concerns about your health are a mixture of things that you probably don't need to worry about, and some things (like your pinched nerve or sinus infection) that are "real," and need addressing.
As best you can, keep yourself healthy and well until you can see the ENT. One of the best ways to combat health anxiety is to get solid medical advice from a trusted professional that can help put your mind at ease (and not doing the self-diagnosis through Dr. Google, which I'm definitely guilty of. That will help you sort through the fact from the fiction.
We don't discuss specific medications here on the forums, but I can tell you that if you have been given an antidepressant for your anxiety, which is quite common, three weeks is only the beginning of when you would start to see results. These things take time to build up in our systems, so hopefully things should get a bit easier for you from here on out.
I think health anxiety is best addressed on a case-by-case basis, as sometimes the anxiety is warranted and sometimes it isn't. Sometimes it's about our own health, sometimes it's about that of a loved one.
Without being a medical professional, I can say fairly confidently that a pinched nerve shouldn't be exacerbated through movement that aggravates it (unless under the advisement/supervision of your physio). That said, I don't think there is any reason to think that this will make you more susceptible to other things getting "set off." Our bodies are designed to move and articulate in all sorts of ways, and for the most part they do a pretty good job of it. Might it make sense to try some light stretching or yoga early in the day just to get yourself used to moving around?