Yes Womble bad backs can be v debilitating and restricting. I'm a GP myself and have had several bouts of severe back pain over the years but fingers crossed not since I started in small-holding about 2 yr ago perhaps because more physically active. The way that it has affected me is that it can be triggered by a seeming minor episode of inappropriate lifting - you feel it go - it's not too bad this time I think (I Hope!!!) - I keep moving that day, go to bed at night and overnight it stiffens into a situation where the slightest movement of the back sends agonising spasms through you and it takes about half an hour to actually get out of bed in the morning attempting to hold the back in as near a rigid position as poss while moving the limbs miniscule amounts at a time. A few days of that and it gradually starts to settle and I can start to do stretching exercises, and it settles over 2-3 weeks. So in that way it does not sound like yours which has gone on for months. In between times I appear to have no restriction in the amount of weight I can lift or move but am careful in the way that I do it.
I went to see a physio in our occupational therapy dept after my worst bout, and what she said made sense at least in the way it affects me: the back can be primed to 'go' by prolonged periods of flexion and this can be for example sitting in a car seat, prolonged sitting at work, or bending over to do some task such as weeding, or on one occasion for me scraping pain off window frames.. Then following this the back can then go if you try to lift something - even a very light thing - in an inappropriate way ie in a position of flexion. After prolonged bending like this you should always do some extension stretches ie leaning backwards (the lumbar ie lower part of the spine is extended backwards) or the exercises below. You can put a rolled towel behind the lumbar spine in your car-seat or your work chair to maintain a better position of the spine, though newer car and work seats are being made better shaped, or adjustable. When you lift things, even light things, don't lean over forward. Bend the knees and hunker down, keep the spine straight and lift by extending the legs; in particular don't lean the head forward at the neck, but put the head back at the neck in the way you see weight lifters do it when they lift.
These are the exercises I was told and which do seem helpful:-
1. Stand in a door way with the door open, left your arm up sideways so that the elbow is touching the side of the door frame and your feet are set at hip width apart. Tilt your pelvis sideways trying to touch your hip against the door frame, keeping your elbow out horizontally touching the frame. 5 times slowly one way then turn round or move sideways to the other side of the door frame and tilt the pelvis the other way. You will readily find if there is spasm in the muscle of one side of the back that one way is easier than the other (the first time I did this exercise it really brought home to me how much spasm there was on one side of my back compared to the other)
2. Kneel on the floor, then lean forward so you are resting on your straight arms ie you are like a quadruped. First with one leg, lift the knee off the floor and extend the leg back so that it is as straight as possible and then flex that leg forward so that the knee as near as possible touches your chest, then back and straight again, then flex forward again. Slowly back and forward 5 times R leg then 5 times left leg.
3. Lie on your front on floor, the push your arms down on the floor in the way you would if you were doing a press-up but leave your hips/pelvis on the floor. Do this 5 times. The movement of the upper body away from the floor is quite restricted at first but improves as the days go by.
Do all these slowly and with good form at least 3 or 4 times a day; as the days go by the range of movements will increase.
You should do all these exercises always every day in life but of course like anyone I stop doing them once I feel better. Always be concious and careful how you bend and lift. Some tasks can be adapted so they pose less risk eg I do weeding kneeling rather than bending over. Digging is high risk for me but Ok if I watch technique.
Painkillers :- I only take paracetamol - though I often prescribe all these other things to my patients I am too frightened to take them myself eg tramadol (this often seems to send people doolally), diclofenac, diihydrocodeine (low strength cocodamol ie 8/500 or Ibuprofen are probably Ok but i prefer to avoid them). Painkillers work better if you don't take them very often.
Generally i feel best advice comes from physiotherapists.
OK sorry a bit of a long post not sure if too relevant to you David as your pain seems a little different but hopefully might strike a chord with someone