Sparrow, if you can, go see a physiotherapist and take any medical information (x-rays etc) about your back with you. A physio generally knows more about this sort of thing than doctors and will be able to advise you of specific stretches and exercises to strengthen your back and prevent pain while you wait for disc replacement to be a possibility. If the physio knows about cycling, even better. To find someone good, ask the guys at the bike shop for the name of someone who is popular with the local cycling community. You want to be able to ride without this pain resulting or else you won't enjoy it.

Good luck!