Sorry to hear! May you have to accept that to return to work can be hard? I don't say this to be mean, more like, if you lower your expectations, may be it will become more easy to live with your tiredness. I used a half year once to get accustomed to work. That meant that I went to work every morning and came home exhausted every evening. I ate my dinner and rested for a couple of hours, before I did relaxation exercises, ate something and went back to bed for the night. I thought the tiredness should never leave me, but it did.