How do I prove to someone ?

How can I prove to someone that I’m worth his time ? That what we have is good and he can’t just throw it all away.

My ex and i were together a long time and spent alot of time together. We soon got sick of one another so we decided to give one another space. It helped alot for our relationship because I got to do what I wanted to do, as well as he did. But now the little thigns I do makes him tick. He treats me like his girlfriend still, but at the same time treats me like shit and talks about me to all his friends.

It’s like he is two different people. I just want to show him that we are good together and he needs to realize that, how can i get that through to him.