Help me to understand him?

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I am currently 21 studying in the UK. I've been with my boyfriend for 7 months now- everything is perfect-he is the perfect guy who tries for the best- treats me right and takes care of me.
However, i am still thinking of my ex.We met when i was 17 (still living at home) and it lasted until about I was 19.5. The relationship was rocky and up to this day i cannot understand whether he had feelings or not.
When we were together he used to ignore me and then when i left him always used to try to get me back and i have even seen him crying, trying to get me back or in fear of me going with someone else.
Long story short when i got with my boyfriend a month after he got with his current gf!I had his gf on my fb but not him so whenever i used to post something with my bf immediately something with him and his gf was posted on her fb!.( Mind you i didn't think about him at all before he got a gf,it started when he did)
I added him a month ago and a few days ago he started liking random posts of mine including a picture of me and my bf.
I would like to know why is he acting like that? What's his purpose?Isn't he happy?
I want to forget the whole story but I feel the only way to do so is by those questions being answered..