What can cause leg and buttock pain that gets better with walking? i cant sit for too long without either hurting or tingling. usually one leg

Sciatica: Although there are some other possibilities like muscle spasm and pyriformis syndrome, the most likely cause is lumbar disc disease with nerve impingement. To be sure see a spine specialist or PMR doctor who can order neuroimaging and a test like an EMG. Then the next steps after making sure there is no vascular, immune or rheumatologic process would be to initiate PT & possibly meds or injection

Be seen: Though this is likely a muscular problem, it could also be related to nerve of blood flow ("claudication" or "pseudo-claudication"). Talk to you r doctor about these and the other mentioned muscular conditions