I am with Coach May.
Baseball is a game of adjustments, if you are losing sleep over this now, I can't imagine how you will feel as he gets older.
Maybe he isn't ready for playing on a team with better competition. If he is feeling pressure, you need to change the team. 13 year olds should not be down on themselves because they are struggling.
At 13, your son should be HAVING FUN. Parents should be HAVING FUN.
Sorry to get on your case, but what are you going to do when he gets to HS, or college and he goes 2 for 9?
As coach says, no one cares what you did at 13.