I wrote a post in this forum a few months ago, when everything was still kinda fresh.
To give a brief summary: my dog, Fox, had several prolapsed discs and got paralyzed in his hind legs. In the beginnig he couldn't pee, wag his tail or walk. Now (9 months later) he can pee, he can somewhat control his poo and he can somewhat control his tail. He can't walk but he has feeling in both legs. We still go to physical theraphy once a week and do some exercise at home. I still have some hope that he might walk again. This whole thing is and was emotionally and financially draining.
I am now at an point where I would like to buy a wheelchair for Fox. My physiotherapist recommended someone to me who does this professionally and is highly praised for it. Some people in my family said that I should wait, because the wheelchair is very expensive. But I can't walk around with this carrying aid anymore (my back really hurts!). And I also want a little bit of normalcy again. But of course I still worry. What if I only need it for a year? Or less? What if something else happens?
And then there is this thing where some days are better and some are worse. Since his surgery Fox had days where he felt bad, which is normal I guess (the doctors said so). But since monday he isn't lifting his tail anymore. It didn't worry me so much on the first days, but now a few days have passed and he still doesn't move his tail. He couldn't really control it all the time since the surgery, but if I had food in my hand he would wag his tail. Or when we went for a walk he would always lift the tail up high while walking - but not this week. He also seems kinda tired and sometimes a bit grumpy. I gave him a massage and checked if he was hurting anywhere, but he seemed fine. When we went to therapy he was also fine and the therapist even said that the cramp in his leg was almost gone! He eats, pees, poops and plays. I wondered if it may be related to the weather, because it became very hot this week (25-30 C / 77-86 F) and he always gets somewhat tired when its hot. But this wouldn't explain why he isn't using his tail anymore.
Maybe some of you experienced something similar? I mean, healing isn't always a straight path and maybe it's a small setback. I'm just so, so worried something horrible will happen again. Thanks for reading!
Let them try it for a week and they will understand. If your back gets bad enough, you may have to spend money for personal physical therapy. I had to go to physical therapy for my back after my golden retriever passed. It wasn't cheap. I had been helping him for about 3 years total, especially the last 8 months. I had been lifting him for over 2 years before he got a wheelchair, because for a long time he just needed help getting up, then he could walk, so I didn't buy one till later. Anyway, all the lifting adds up. And I should have started taking an anti-inflammatory for my back 
If you are not taking any over the counter meds for your back, you might want to consider it. Naproxen helped me, but you might have something different that you prefer. The problem is, you are so focussed on your 
Is it possible he needs his anal glands expressed? Could they be bothering him? The only other thing I can think is perhaps he has some pain that is not showing up when you palpate him. My dog had neck pain that was missed by several doctors (and me) but it was definitely there. It seems like your physiotherapist would locate pain if he had it, but I don't know. I had 2 vets and a board certified neurologist miss it in my dog. Seriously.
I hope you will post when you find out what was causing it.
Ohhhhhh. That can become serious. It sounds like it already is serious. I don't know why your family is suggesting you wait. It could become worse and require surgery. This is really not funny. Reality check. Don't let anyone underestimate the seriousness of a ruptured disk and prolapsed disks. If my back was like that, I would be very, very concerned. You don't want it to get worse. I am worried about you, and I am also worried about your dog if (Heaven forbid) you can't care for him. 
Since he has feeling in both of his hind feet, maybe he will walk again someday. Perhaps he can practice in the wheelchair. There are 2 ways to use the wheelchair. You can put the feet up in stirrups so he only uses his front legs. Or you can leave all 4 feet on the ground so he can feel the grass and maybe use his hind legs a little. 
The wheelchair has a harness in front that has to be connected to the back part where his legs go in. I can also adjust the height of his legs, so he can be stimulated a bit or if he can walk again I can let his legs go down completely. 