Deepest sympathies 
it must be so hard for you.
DD's 22, she's been just about physically non-functioning since Nov as well. It's concerning me so much that I'm keeping a daily journal of her symptoms and capabilities. She also suspects her symptoms are getting worse. Fatigue and pain doesn't come close to describe her daily life. She does sleep but wakes up shattered and often has brain-fog, sometimes on waking, other times after a few hours. Having eliminated lots of possible causes, I'm seriously wondering about gluten ataxia, that's our next thing to try. I've tasked her with trying to find a week's worth of recipes for herself as she already has a host of intolerances and dp is ill so I've been torn between caring for both of them since Sept. If gluten ataxia isn't it, then I reckon sleep apnoea is the next thing to rule out because since birth she does stop breathing for a good count of 10 periodically during the night.
She can't describe the pain very well and she's often very cold. I'm in a t-shirt and leggings, bare feet in flipflops, central heating's on, aga's on, she's wearing fluffy bedsocks, fleece pyjamas, jumper, a thick plush dressing-gown and has a hot water bottle and at least one cat.
We find these help in varying proportions depending on the type of pain and what's affected.
TENS machine, like the ones used in labour, it can block the pain signals from the brain and gives some relief sometimes. She finds it most effective for nerve-pain.
A long soak in a warm bath with 3 good handfuls of the Pink Himalayan Salt, I don't know what it is about that particular type but it works for us like nothing else can.
Massage the affected area with warm oils and any essential oils of choice, there are plenty manly ones like sandalwood, black pepper etc.
Microwave hot water bottles.
Warm drinks, relaxing herb teas. No junkfood or processed food.
Splints for affected joints.
All sorts of fluffy fleecy comfy day and night clothes, nothing tight or restricting. Knee warmers, ankle warmers, neck warmers, hand warmers, fingerless gloves.
Bed is an ordinary mattress with a memory foam topper and a Dunelm Mill Teddy duvet, (pale cream colour, it's cuddly like a teddy, has no bears on it,Google their Teddy range) I keep saying it's like sleeping in a cloud 
In summer I use a mulberry silk duvet so it's cool for her.
All sorts of posture aids and cushions and throws on her half of the sofa to encourage good posture but also give comfort.
Aero Pilates machine with rebounder to take the strain off joints.
Salt lamps for negative ions.
Cushioned mats to make standing a bit easier, 2 garden kneelers gaffer-taped together is still small. I've just bought a very padded fitness mat in Aldi which I may use double in the hope she may stand in the bathroom long enough for me to wash her hair over the basin.
We've had very varying results with exercise. Despite logic saying gradually building up stamina by starting small and doing a little more each day, it just doesn't work. she decided to try last summer to see if she could walk a little without too much pain. Day 1 she got as far as next door but one and I nearly had to carry her back. Every dry day we did a little more and eventually she managed about 100 yards. The day after that, she was back to only a few feet 
and hasn't made any improvement since.
Hopefully that may give you a few avenues to explore