Just because he sends you a message, you are not automatically obligated to respond. You've been through this over and over and over and over again. If you're ever going to get healthy, you have to decide that enough is enough. If these texts are dragging you back, then it's time to go NO contact and block him. He's an EX for goodness sake. He's an adult, he knows what he needs to do!! He's not truly asking you, he's just trying to find a way to hook you back in.
Let go or be dragged......