You should go and see your doctor about your current back pain or consult someone like a chiropractor for advice. In terms of mattress choice and other issues, these help sheets may be of assistance, but it is important to get to the root of your current pain first. http://bit.ly/aAdWrh http://bit.ly/9XFkk6 http://bit.ly/bPJ9Si
theres allot you CAN do,but that may not say much about what may be done.
first dont wear stupid shoes!
second, work on your posture.
and yes, i'd think the mattress should be closer to the harder side.
now tell me, if you look at your feet(yes your feet! & ankles ) would you notice maybe your toes are pointed slightly upwards a flat arches or very high & curved, perhaps a protuberance on the top of your foot or perhaps the sides (look up healthy feet vs the one's that are not as healthy{and i dont say that as a sickness!} then take a look at yours...)
and here's the fun one, is there an inversion of your ankle (in a way foot), and by what degree?
would you consider any of your joints extending to much,let's call it and interesting angle.
consider your weight and how your build might affect your posture...
all these silly things i wrote, are a good place to start asking about.
do some physical therapy that helps me alot