Have you had an MRI of your back. Sounds like it could be a herniated disc. I have bad back and disc problems and they can cause back, side and stomach pain that can be excruciating. What kind of doctor are you seeing. Maybe try a neuro.
27 years old
1993: T1 to L1 fusion due to scoliosis at age 17
2000: Tore and ruptured L4 L5 & L5 S1-it finally got better after about a year. Did really well for about a year.
June 2002: Had a relapse and tore/ruptured disc again.
Now I'm 14 months into it and the pain is still there.
Can't deal with it anymore so I'm having a discectomy in Sept. Hoping and praying that it takes care of my problems!!