I hate the thought of him moving on

I still love him and it hasn't been that long. Why does he seem so fine? Why am I the only one hurting? Why is he posting on his socials, hanging out with his friends? I don't understand why I'm hurting so much and he can just live his life. Maybe he's just keeping appearances, I don't know. I just want to text him, I want him to give us one more chance. I feel so lost without him. Just the thought of him with someone else makes my stomach turn. Did 5 whole years mean nothing to him? How can he give up so easily?