I have chronic Back pain also and iNsonia,I got my medical MJ card for my back pain though.
I havent been able to get any weed for about 3 weeks now,its dry out here and cant seem to find anything,I was taking my left over meds from before,but they have run out,So I just been drinking kava again,it does the job,but you gotta drink alot.I drink about 2 gallons a day.I sit in my back yard with some reggae adnd just mix.....its not as easy as weed,but it's legal and it works.