Prostate removed and fatigue

I had my prostate removed in May 2017. I started to feel fatigue around the second month. This is now seven 7 months later and I find it hard to concentrate or motivate myself to do things I generally enjoyed without getting at least 11 hours of sleep each day. On my off days from work, I can usually sleep 16+ hours straight. I hate having to sleep this much. After my sleep, I wake up and feel generally lethargic at best. They say exercise will help but I physically can not workout because of my fatigue. My doctor says it will eventually go away but 7 months now and it is just the same if not worse. Any suggestions on medications or maybe a suggestion on how you got better.

Thanks,
Brian