Years ago, when I was in the hospital for a few weeks, I came home almost 20 pounds lighter. As I was in weight loss mode I thought it was great, although most of it slowly came back (as it was mostly water). The doctor ordered me to maintain for at least a month as it was a compromised immune system (in his opinion) that had landed me there in the first place. The comments were that I could not eat too little, exercise too much, and sleep almost not at all and not expect it to affect me.
Take your medicines, listen to your doctor, drink plenty of fluids - and get better soon.