The pipe that leads to the backyard is on but there is no water coming out. Lately the valve has been turning but not shutting off- it was no big deal since I shut it outside. Now both valves are open and there is no water coming out. What could it be?

Sounds like you need to replace the valve. If it turns but does not shut off it could also turn and not turn on. Question, if it turned but did not shut off how did you ever get the water to stop last time?