Right now you are not well. You have an illness and need to allow yourself time to get well. Blaming yourself and thinking you should be better is a type of thinking I get stuck in too, and it doesn't help.
Would you feel this way about a friend who, say, had cancer and could not work? Would you blame them? I think you would like to support them and be understanding of their difficulties.
Give yourself the same support and respect.
You deserve it.
You will get better, but need time.
Take the pressure off and allow yourself to need time off and support.