fibromyalgia and joint surgeries

I am a 76 year old woman and was diagnosed with fibromyalgia several years ago. About 3 years ago I went through knee replacement surgery and it required a much longer rehab than when I had my first knee replacement before my fibro diagnosis. Did anyone else experience this after injuries or joint replacement? i'm now in another situation... I tripped and fell at home resulting in a dislocated shoulder and a fracture. i have had the repair surgery and about two months have passed and I am still in considerable pain. If I have nerve damage, would this account for my heightened pain level? Now I'm worried about how painful rehab for this will be! Any advice??