what should i do in this terrible situation ? I am depressed because of my ex boyfriend?

[Sania]

I was continuing sort of friendship with him (ex boyfriend).
He was behaving good to me , but suddenly he has chnaged. He used to treat me like an option , wasn't interested as much i was, i always kept chasing him and mostly, i was the one to initiate contact to him.
Now suddenly , he has stopped texting me himself and has started ignoring me. It is hurting mr now. He always does this to me and when i say him all that , he says i am important for him , he cares for me , he doesn't want me to leave him , etc.I don't get him , if he wants me still then why he treats me like this.I did text to him two times but he was quite rude, he talked to me in just two messages (uninterested way).
I'm caught in a fog of depression and I just don't see the light at the end of the tunnel. I feel like I will never feel normal again. I don't feel like myself anymore, and all logic is gone.

Do i need to leave him all alone now ?
Cut off all contact on social media , mobile /?
When i decide to leave him , he doesn't let me go and says he wants me not to leave him ever , i am an important part of his life.