I believe when your body is stressed from lack of sleep, nutrition etc you come down with virus and illnesses easier but it seems more like your concern is about how you react to what people say and think.
You obviously have a good work record and have earned your sick leave. You have your physicians to back you up so I would try not to put to much on what your bosses are saying as this is causing you anxiety, IMHO. I seems to me that you are a very valued employee and your boss is lucky to have you.
You may be picking out negative details and dwelling on them exclusively, so that your vision of all reality becomes darkened. Attempt to turn this thinking around and look at the positives.
I hope you keep posting and I wish you peace.