So why do I get serious anxiety and some depression over things I cannot control?

I completely understand how you feel. You are committed to your job and there is nothing wrong with that. Your supervisor should be grateful to have you as an employee. At least you are making an effort and believe me, they all can see that. If you are sick, that is something you just can't help. Maybe you should see a doctor just so you have that as a backup to prove that you are indeed sick. And if you keep leaving the house and going to work, that will slow down your recovery time. And if you are stressing, that is not helping you to get better either. See if you can get something to help you sleep or try drinking some Chamomile tea to relaxe you. (I hope I spelled chamomile right.) Anyway, good luck to you. Talk to your supervisor about how you feel. That could help you feel more at ease as well. Especially if he or she is understanding. Hopefully so. :)