Guy's Behavior

Why did he all of a sudden stop liking my Facebook posts and stop talking to me on Facebook chat?

Ok, me and this guy do have a history: we had a bit of a fling a while back, but we're still friends. It ended because he said he only saw me as a friend, although it was obvious before that he had feelings for me, but maybe those passed. He now has a girlfriend and even though I'm jealous, I never let it show and just act casual and normal (maybe you should also know that I always suspected that he still has feelings for me as I do for him, but I could be wrong especially with this new girlfriend) He is very active on Facebook and likes just about anything from me but also from other girls and guys. Whenever I send him a pm on Facebook he also answers right away. Now he all of a sudden stopped answering after I send him a reply on Facebook chat (nothing insulting!) and also stopped liking my Facebook posts. What's up with that? :/ Because he still likes other people's posts.
Why did he all of a sudden stop liking my Facebook posts and stop talking to me on Facebook chat?
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