Advice. I think I know…

Hi,
I don’t know if this is the best place to ask but anyway.
I am 27M, I broke up with my ex over a year and a bit ago (27M). The reason was because it felt like roommate situation after 5 years of being together. I’ve been in contact on and off, because I still cared about him. I still had feelings because he was my first partner, he taught me so much about myself, we got a dog while we were together (main reason I kept in contact).
I recently found out he was seeing someone (which I know was going to happen), but I’m jealous and I feel like shit just knowing. I definitely need to work on myself and grow. My question is should I block/delete him from everything? How do I move on? I thought I moved on but all these feelings are coming back.