Multilevel fusion for degenerative disc disease-am I nuts?

I am 29 with really bad degenerative disc disease on three levels S1-L4-5. I have tried everything, physical therapy, pain killers, exercises and nothing works. I'm scheduled to have a multi level fusion at the end of the month and I'm scared out of my mind. From what I have read this extensive surgery is rarely done, but my doctor thinks it will help. I just want to feel my age and be able to walk around . Am I crazy for doing the surgery?