I have had three lower lumbar surgeries and one of them was a fusion. it seems like every 2, 3 years my. back starts hurting bad again. why is this?

Exercises : I do not know the level of your fusion or the # of motion segments involved. But following three spinal operations in the same area will result in scar tissue formation that may account for some of your pain. Lack of core muscle strength may also contribute. The development of adjacent disc disease above or below the fusion may be the cause. You should see a spinal surgeon.

Bad luck: One surgery may lead to a second and so on. Other levels can break down. Complex question needs a careful evaluation with specialist to address your specific issues.