Am I right to feel this betrayed?

Sorry this is a bit long but I need to let it out. My ex of 4 years and I broke up 2 months ago. It was smth mutual before we got hurt even more. We love each other but it wasn't the right time, so we said after some time, we'll be good friends and maybe in the future try again. He reminded me constantly that he didn't want me out of his life and if I decided to start smth with someone else, i wouldn't post it so soon bcs that would really hurt him. He's a very social media guy and I'm not. I told him I was gonna stop following him for a while bcs It would hurt me to see his posts everyday and so I did. We didn'talk for 2 months and 2 days ago he called me crying that he missed me a lot, that he wanted to get back together, that thinking about someone else touching me was killing him. That if we could make a pact not to sleep with someone else until we were really sure about us. To be in each others life at least as friends. I told him I didn't want that, it was not healthy for any of us and we both decided to break up for a reason, but i could agree to start with our friendship and talk once in a while. We even plan a date in 6 months! We finished the call and i was so happy. WELL, yesterday I found out that he has been already seen someone for the last month. He posted stories with her, kissing her and going out with his friends. I did a little research and I found love comments and heart reactions. I feel betrayed. I feel he broke my trust. I know he was in his right of going out with others but to post it and make it public and then calling me and tell me all of that was just SO hypocrit and cynical. Today I called him, he said he didn't intent to hurt me and he didn't intent for me to see that but he wanted to keep in touch with me. I told him he hurt me and lost me for good. I blocked his number and cut all communication with him or his friends. I feel heartbroken and so angry, and naive and I've cryed a lot but keep thinking, maybe he was in his right to do that bcs we we're already broken up? What pains me the most is that he asked me constantly not to hurt him like this and take care of each other and HE DID IT!