Walking with my daughter and got a sudden burst of extreme pain in my abdomen from belly button down. What would cause it. Brought me to tears?

Musculoskeletal. Sudden, extreme pain is almost always caused by muscle irritation. That's the good news. You likely pulled an abdominal muscle, and these, especially the obliques, can be very painful. Put ice on area first 2 days, then switch to heat if pain persists. Do some gentle stretching exercises and avoid heavy lifting. Can use Ibuprofen if pain hard to tolerate.