I'm guessing, and this is just a hunch, that it means he probably finds it embarrassing to say, "I love you."
Lots of guys have weird hang-ups about saying those three words. Personally, it doesn't freak me out at all. But some guys think it makes them soft if they say them (as KRS-One notes in his classic rap song, "Love's Gonna Get'cha"). Some guys are worried they're going to be left hanging after declaring their love (there is a good Seinfeld episode about that), and some dudes are concerned about not being able to live up to the promise of those words (remember, we're children of the divorce generation—we grew up seeing a lot of parents who said they loved each other prove otherwise in very legal ways).
So maybe he's got some issues around saying, "I love you," or (sorry) maybe he doesn't feel the same way for you that you do for him. For all I know, you're asking him to pledge his love for you during the jousting match at Medieval Times, and he is understandably embarrassed.
If it really bothers you or makes you feel uncertain about where you stand, then talk to him about it; alternatively, you might suggest that he write it down and pass it to you in a note.
