Why does he do this

My bf was very loving and attentive in the beginning, then the fights started happening. He started being distant and off and easily irritated by me. I knew why, I always started fights so I get it. But I thought it was going to get better and just felt like I was begging for his attention and for the bare minimum effort. He just wouldn’t. He kept being hot and cold. I’ve tried leaving several times bc of the coldness from him but he promised he wouldn’t anymore. Finally today I gave up and said we need to go our separate ways, I wished him well and he seemed fine and like he didn’t care. Then.. he starts blowing my phone up. Like what? He only does this when I want to walk away. But the coldness never changes. What should I do? Why is he doing this?