Do you have an iPhone? If so, go to your text messages and swipe left and you’ll see a pop up for “Hide Alerts” and it will “mute” him. You won’t get a ding or buzz when he sends a message and you’ll see it when you happen to check your messages. I’m telling you just not jumping when I hear the phone has made a huge difference for me. If you have another brand of phone I’m sure you can still achieve the same effect and hopefully someone can provide some input.
Hang in there, just get through today. You are worth it.