i'm not sure what happened to mess up your back) but when i was an avid gardener, i think my back was pretty much always sore, so i had to learn how to figure that stuff out. well, that and being a very impatient single girl who doesn't like to wait until she has help before moving stuff.
anyway, if your lower back is bugging you during bedtime, one way you can take the pressure off your lower back is by bending your knees, and supporting it with a pillow (if you're a back sleeper). for example, take one or two pillows (depending upon the fluffiness) and put them under your knees. you might have to figure out the configuration by playing with it, but you just need to get a bend in your knee.
also, since i'm a stomach sleeper, that was around the time that i had to learn how to sleep on my side (sleeping on your stomach is kind of verboden if your back is messed up). if you're a side sleeper: one thing that helped me is putting a pillow between my legs which squares your hips and can take pressure off your back too. i think that's around the time i got a body pillow, which worked for the leg pillow configuration.
hopefully you have lots of pillows--though, i've noticed that it's pretty much a requirement for being a chick. try to be mindful of having some body alignment when you're sleeping, with your head, hips and knees all facing in the same direction.
p.s. if you're having chronic back problems, you might want to work on your core and flexibility--which are kind of opposing sides of the same coin. i recommend pilates, which includes lots of core-strengthening and flexibility stuff. it resolved the vast majority of my random back stuff. : ) and if you need more help, you know how to find me. ; p
one more thing: i know you're not much about pharmaceuticals, but this would be a good time to consider an NSAID, if you're not taking anything for pain and inflammation. of all the NSAIDs, aspirin is the most "natural" and mild, from naturally occurring salicylin found in willow trees. the payoff is that they help with pain AND inflammation which is why they can promote healing.
i hope this helps. also, i'm praying for you. : )