Hi Hoyt - I take Celebrex - dr. Rx'd it for 200 mg/twice a day, but I usually only take 1 a day, as it tends to eat up my stomach when I take more. (I also skip days sometimes if stomach feels at all not right). It is an anti-inflammatory, and yes it is prescribed for arthritis, but also many back-pain folks take it and get some relief. It doesn't do a whole LOT for my back, but I think it might help a little - I take it mostly for my knees (arthritis) and feet (arthritis and recent surgery). Be sure that you take it with food or milk, and that should help prevent stomach upset.
I also have DDD and have had two 3-level fusions, with additional discs going south as well - no fun - especially for someone as young as you! (I've had on-and-off back problems since my teens, but never got MRI/diagnosis until about 5 years ago (then-aged 38). My dr. told me that even *I* am too young for my spine to be in the shape it's in, so you are really young. I'm sorry you've got this problem so early.
I'm not familiar with the other meds you mentioned, except flexeril (muscle relaxant), which didn't do much for me either. You might want to ask your doc for a referral to a pain-management doc, who may be able to help you figure out a better regimen for managing your pain.
Good luck!
JD