He may have told you that you don’t love him nor want something serious with him because he may feel as though you are just in the relationship for fun and nothing more.
Perhaps he gets the sense that you don’t believe that you have a future with him.
He may have gathered this opinion based on a nonchalant or casual attitude on your part when it comes to your interactions with him.
He may feel as though you never seem as though you are truly engaged or that you even want to get to know him on a deeper basis.