You didn't mention where you were operated on, but I would guess that it is the lower back due to your mention of your sciatic pain.
I dealt with lower back pain for 3+ years until I finally went the surgical route. The first thing I did was ask my wife (who was a Recovery Room Nurse) to find the name of the hospital's best surgeon. After finding out that you don't want an orthopedic surgeon playing with your back I was told to see a neuro-surgeon. After some minor manipulation the neurosurgeon who was recommended to me determined that I had a bad disc at L5-S1 (which was clearly verified by the results of the MRI I had done later) and suggested that I have the disc surgically removed. The neurosurgeon I visited for the second opinion said the my situation was clear cut and that I needed surgery.
To make a long story short, I had the surgery. Two days later I drove myself home from the hospital. Three days after surgery I was coaching my men's baseball team, and the following evening I was at Dolphin Stadium watching a Monday Night Football game. Two weeks to the day later I was doing aerobic exercises, and one month to the day later I was playing baseball again - pain free.
Like the others mentioned, I believe you should seek a second opinion from a highly recommended neuro-surgeon. IMO, with my experience, there is no reason you should still be having the problems you are. I would expect that another MRI would be in order as that should clearly show what your back's current situation is.
Do not put it off any longer. Back pain is nothing to play with, and the longer you wait the better the chances that you could do some irreversible damage to your nervous system.
I hope things work out for you as I know that living with back pain can be a miserable experience.
Good luck and keep us informed,
fantum