Ambiguous Love, Heartbreak

Why is this guy like this?! He already has a girlfriend, but he treats her so well, giving her endless false hopes and wild imaginings. He says he has no time to go out with his girlfriend, yet keeps asking her to come over and work on assignments that get nowhere. He even spends an entire day taking her out for Häagen-Dazs. His actions are born of affection, but he never crosses the line. He doesn't do anything inappropriate. But that heart-fluttering feeling... Is it really just an illusion? Ambiguity really is a terrible thing.