I have lower back upper buttocks pain that starts with a burning that gradually increases to a painful burning. It hurts only when I'm sitting, and when at its most painful gives me a feeling like my butt cheeks are being pryed apart and I'm sitting on bone. I went to a doctor and was told it is not Sciatica, and that it is a muscle issue and that stretching therapy to improve my flexibility in my hamstrings, and strengthin my core will help rectify the problem. They also said that poor posture for the 47 years of my life is a contributing factor. Can anybody shed some light on this and some possible remedies?