I'm open to recommendations if anyone could offer their expertise. Three doctors have examined me and concluded that my feet are different lengths which cause

I'm open to recommendations if anyone could offer their expertise. Three doctors have examined me and concluded that my feet are different lengths which cause my back pain, but I can't afford any customized insoles at the moment. In my lower back, right on the right of my spine I get occasional stabby pain which prevents a lot of movement. It usually stays away for over half a year and then it acts up for a few weeks but now it's been worse. When I get the initial stab it means that for the next few days it can come at the smallest motion that my back doesn't agree with and then after a few days everything seems fine. Except for the last two months my left back of my thigh is also "stuck". The muscles seem to be fine, it feels more like a pinched nerve. Going to a professional masseuse doesn't help because they can't hit the spots that hurt, it feels more like its in my nerves. My left thigh hurts even when I'm coughing. The doctors I've seen say that I don't have a slipped disc by visual examination but I haven't been scanned. What could and should I do?