MrSteve, I've got five years on you and have been dealing with back pain for more than 20 years. I've seen tons of chiropractors, acupuncturists, MD's, massage therapists and have tried yoga and Pilates (my wife is an instructor for both) and have spent thousands on seeking relief. I've had times where my back spasms got so bad while surfing that I've seized up walking back to my house and could barely move for minutes at a time and spent 20+ minutes getting my wetsuit off. I've done the massive amounts of NSAIDS thing (2400 mg per day, as recommended by my PA friend) as well as prescribed muscle relaxants etc.
For me, with no true back injury or condition (nothing showing up on MRI's/X-rays), but with very real (with quantifiable EMG tests/results) spasms and resultant pain, the only thing that's helped me was a book I heard about on the Howard Stern show. It's a short/weird read and it goes in circles and there is never an "Aha!" moment, but for me and many others, it really get's you thinking and helps with the mind/body connection for overcoming the issue. I've had to read it several times, but when I employ the gist of the book (it's way too nebulous to write here) I've found relief.
I know your shoulder is another issue which is affecting your potential board choice, but my back pain was really starting to affect my surfing. I was hesitant to really whip my body around, free-fall from floaters (the occasional air) and started to surf safe to not aggravate my back issues, which for me took a lot of fun away from surfing. It's not been all smooth sailing since I've employed the book's theory, but I definitely have longer stretches (months) without a hiccup and I'm able to get through the occasional bouts of pain much quicker now. Here's a link:
Healing Back Pain: The Mind-Body Connection [Sarno MD, John E.] on Amazon.com. *FREE* shipping on qualifying offers. Healing Back Pain: The Mind-Body Connection
www.amazon.com