My Fiancee broke/fractured her back several years ago, she was on a see-saw and her friend thought it would be funny to launch her. Ended up not being funny. according to the doctor it was either her L3/L4 or L4/L5 that got fractured. Hard to tell because she was told one thing, but the paperwork says different(she had no health insurance at the time so they took very little care of her).
She describes the location of the pain as being lower left abdomen just to the right of her hip. The pain is intermittent and is hard to say when it stops/starts.