I just don't understand my ex

I need to vent. 😡 Quick overview. My ex and I dated for 5 1/2 years and lived together for 4. We've been through a lot. Family issues, his dads death,  changing jobs, pet loss, etc. I wanted marriage and babies and he did not. So we broke up and I moved out. We tried to make it work after I moved out but it didn't. We both dated another people and I found the man of my dreams and now we are pregnant! I now and then still hear from my ex. The next time I heard from him I decided to tell him that I'm pregnant. He was happy for me. He asked that I stop talk to him. I respected he's wishes. Not 24 hours later he texted me a picture of my cat that passed away, Daisy. It upset me but I didn't respond. A month has passed and I have not heard from him. We are Snapchat friends but I don't look at his and I rarely snap anyways. But today I did, I snapped a picture of my cats sleeping in the cat tree. Of course my ex responded to it and referred to my cat Daisy who has passed. Now I'm pregnant and it's the one topic that makes me extremely upset and I uncomfortablely cry. I didn't let him know that he upset me but I'm sure he knows he got to me. Why do guys do this? He didn't want what another guy can give me? And he asked me to leave him alone and I did. I know I shouldn't care but why is he doing thing? I'm asking you all so because I just don't want to talk to him.