Buttock tenderness on both sides which sometimes shifts to the other side. is this sciatica, herniated disc? im worried it could be a spinal tumor. everything i read say sciatica is rare on both sides?

I agree that sciatica rarely occurs bilaterally. Buttock tenderness can be bilateral if caused by ischial bursitis. This can be caused by overuse in certain activities or prolonged sitting on hard surfaces. I wouldn't worry about a spinal tumor. An orthopedic specialist can evaluate & advise you best

Not feasible to be definitive, but the shifting discomfort might represent sacroiliac dysfunction or even hip problems. Spinal stenosis could be another possibility. Instead of worrying and trying to figure this out, suggest you see an osteopathic physician or a physiatrist, get examined, diagnosed and have this treated appropriately.