Having severe pain in lower left side/back just above hip and nausea. should i go to the hospital?

Generally, yes: If one has very uncomfortable tummy pain, and is normally in good health, possibilities include: diverticulitis, kidney stone (very painful), constipation (crampy), stomach flu, twisted bowel, spine problem, cancer, etc... Patients with severe pain, meaning worse than mild or moderate, need a doctor's evaluation right away to see if a surgeon should evaluate (an ambulance can transport to the ER).