After being extricated from a car after being hit by a drunk driver, I know about back pain - it's a long, slow recovery process.
One of the best programs of exercise is the YMCA Healthy Back (there is a DVD version available) along with Gary Kraftsow's 'Vini Yoga Therapy for the low back...". These programs help you to 'think' of your back as you re-learn to do everyday tasks.
Going without a garden was not good therapy for me, so I started slowly by sitting on a milk crate and pushing a scuffle hoe back and forth. It was a start.
Sleeping position is also important. One of the best positions is to lie flat on your back with the knees bent and the feet flat on the bed. (There are triangle-shaped pillows available if you need one). My cat adjusted to the new position and slept under my knees. No, it's not a great position if you share the bed with another person and a few dogs, but after a few nights you get the hang of it and the back improves.
I don't take things like Advil or Tylenol but I do take Turmeric every day - it is a fantastic anti-inflammatory.
My other go-to aid is to not have the weeds in the first place. I use a double layer of professional quality landscape fabric, Preen, think layer of mulch, and more Preen.
http://www.preen.com/videos/or...
Timing is important when weeding as well. Immediately after a rain the weeds pull out more easily. I regularly pull the weeds from the yards of two of my neighbors (this is my 'stealth reverse-guerrilla gardening' as they do not know how their weeds miraculously disappear).
And if all else fails, a shot of Jack Daniels before a weeding session could help get the job done.