Sorry to hear about your back trouble. You should at least get a x-ray or mri done on your back to see what's going on.
I have alot of the same symptoms as you. The pain in the lower back and pain that shoots down my left leg and hurts foot. But I know what causes it. I have degenerative lumbar spinal stenosis. As well as a bunch of other problems.
The only way to know how to help the problem is to first know exactly what it is. I think you should start a diary of what starts the pain, what relieves it, where does it hurt, how long does it last etc. Do that for a week or so then go back to your doctor and demand answers.
I mean I went through the same thing you did. Except I had a ct scan and got sent to a orthopaaedic surgeon and he explained to me what was wrong in doctor speak. So I had no idea how bad my back was. So I bounced around from physio to a chiropractor as well. It's only through being made worse from seeing a chiro. That I finally woke up and have researched what's wrong with me.
I encourage you to find out what's wrong then research it.