Please help out. I drive my car with a baby and have been stranded 5x.

Did this mechanic test drive the car?... Maybe let it sit and run with testing equipment hooked up and be ready to test when engine stalls... Was this mechanic experienced enough to properly diagnose the problem??... When engine stalls, test ignition spark and fuel delivery systems??? .. If an 'experenced' mechanic can not find the problem with *hands-on* testing... It's little we can help with... useless guesses won't help...Sorry.

might be the crank sensor, it's not real expensive and your symptoms would justify installing a new one to see if it is defective-have him carefully check the wiring and the plug too