Why does my friend check me out when im not looking?

Whenever I look at him or talking to him. He seems as if he doesn't look at me but if I look away and look back fast he's checking me out. We been dating for several months but about a month ago got in a fight. So I feel he's acting like he doesn't look but his body language is like he wants to be near me
Why does my friend check me out when im not looking?
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