Longterm pain relief, what meds have the least side effects in the long AND short term?

I have chronic lower-mid back pain caused by osteo arthritis and degenerative disc disease. I am told by my doctor that I will most likely be on pain meds for many years. Currently I take panadol osteo (3x p/d) and tramadol 200mg (2x p/d) both of these are hepatoxic and not strong enough however I have tried oxy codone and oxy contin but both give me bowel problems and head ache and make me too drowsy to look after my daughter (a toddler) Has anyone got any ideas of what I can try that will be strong enough but with out all the side effects?