Water is running from behind the wall by my tub and I had to turn off the water from outside what could be wrong

You don't say where you are but if the tub is on an outside wall and there is winter conditions then it could be frozen and when it thawed it split. These are messy to fix because you are going to have to take out the tile or surround and also remove the drywall to get to it. Let me know what you find