Struggling, you have to find out "eventually" and the longer you put it off the worse it becomes. At the moment you're afraid of being afraid because you're imaging what "could" happen. That's a good way to drive yourself nuts :-)

Since you're into imagining, imagine something you want? Imagine people are glad you're back. We tend to see what we look for. Look for your job and for people to be glad you're with them and they don't have to do some of your work?

If you were going to be fired, they would have hired someone for your place; have they done that? Are there new hires doing what you're doing? A business wouldn't fire you first and then start hiring. When I mentioned I was thinking of retiring, my company started interviewing, LOL. They didn't want to be caught without coverage for what I was doing. So unless there's someone sitting in your seat, I'd figure out a schedule where you can return gradually, tell people you've had a debilitating physical illness (true!) but you hope you're better now and take it from there.