Suggest Treatment For Back And Leg Pain

I have a problem that seems to flare up about once a year, ususally in the Springtime for some reason. It begins as lower back pain, progressing to sometimes severe pain with sciatica down one of both legs. My latest flare-up was the most severe. I have taken anti-inflammatory drugs from Advil to diclophenac, and muscle relaxers (Flexeril). The strangest parts of this is I can never associate the onset of the pain with any injury, change in excercize habit, strain, etc. It will just start. Stranger still is that almost as fast as it comes on, it can completely disappear. This latest episode has me concerned because at present I have almost NO lower back pain except for what feels like "left-over" mucscle and joint tenderness, but the muscles in both legs (thigh and calf), are stiff and sore almost to the point of being locked, making walking very painful. However, this lates episode is also the longest, lasting now for almost two months total, starting with dull low back pain, progressing to almost crippling pain, the regressing. What could this be or what should i ask my doctor to do? I have not had MRI, but a chiropractic x-ray showed plent of space between my vertabrae, so it seems not to be disc related. I am, however, "crooked," and it seems the joint between the base of my spine and pelvis is somehow rotated out of line.