I need advice on my current situation -ex boyfriend.?

[Shannon]

Okay, so this is probably going to sound really lame, but its confusing and constantly on my mind at the moment and its making me act weird with my current boyfriend who i've been with for a year and a half.

So a week ago I fount out that my ex, had started following me on instagram, now this is very strange considering 4 years ago(when it ended) he wanted nothing to do with me and wiped me from his life.. he then got a girlfriend who my friends told me he was with for about a year and they recently broke up. SO now he's following me on instagram (this is like facebook, but you post pictures instead of status' its a mobile phone app for anyone who doesn't know) and occasionally either once a day or once every two days he will like one of my pictures.. is he doing this because he likes my picture or does he want me to talk to him? I wouldn't know what to say or what but its really confusing. Me and my ex were childhood sweethearts. we broke up when i was 16 and im now 19.
I just need a little light shining, am i thinking too much into it or what?