What do I (27F) respond to him (30M)?

My narc ex and I got in a huge fight after he contacted me only a few weeks after we ended. He not only broke my peace and healing but he to date has never taken accountability for all the pain he put me through. He went on to say I do not understand his mental health struggles, but I responded by saying I am the one who knows his struggles the best, I have always been there for him and run to see him when he needs me. Then he sent me this text. How do I respond?

And for those who might tell me l am the narcissist here, I have always emphasized and gone above and beyond for him. I know my texts might come across selfish but I truly don't understand how the man cannot understand my pain? That's why I sound like that.