I have major pain in my lower back down my left leg n butt cheek. got xrays, it not a slip disc what can it be?

Pinched nerve ?: See a neurologist, may need EMG ncv, mri, vascular study etc.

Sciatica: What you describe sounds most consistent with symptoms of sciatica. The sciatic nerve roots exit at the levels of the lower lumbar spine and compression or irritation of the nerve roots causes symptoms. This most commonly is related to disc bulges or herniations and/or other arthritic type changes at these levels. Plain x-rays do not show discs well, and MRI imaging may better visualize this.