When I was at the worst of my depression I felt numb and void of emotion. It wasn't a result of my medications.
Everything that you're feeling is typical of depression. You'll find many of us also suffer from chronic pain. It's hard to be in pain all the time and not be depressed. I suffer from chronic daily migraines.
I found a psychologist that specialized in chronic pain and depression. She taught me some relaxation exercises that helped me reduce the pain and some cognitive behavioural techniques to change the things I tell myself so that they're more positive.
Keep perservering. You can overcome this.
Coquitlam55 (aka Nicky)