Netiquette

Someone who used to be close won't talk to me. What do I do?

So I have been friends with this person for 10 years over the internet. We met on one furry site in a group, and our relationship quickly grew. Soon enough we were mates, then he left the fandom, then he came back and we were mates again, only for me to have to go live in the ghetto. When I came back we were best friends, then he stopped coming around as much. It worried me, and with the onset of my anxiety I had a panic attack and told him I loved him. This was a year and a half ago. Since then he barely even talks to me, and has been spending alot of time with others and short changes me whenever we DO talk, with responses like: Yep. Sure. Uh-huh. And quick to get angry. He is like family to me and I would do anything to get him back, and I know he thinks of me as clingy. What should I do? He is tired of my apologies and any attempt at trying to fix it makes him think I am having a breakdown.