feather_Yewfrost -- listen to @Despotic Ocelot -- even though he isn't an INTJ, he has some good advice.
INTJs *need* recharge time regularly; and if they hit a rare down patch where they are actually depressed, and not recharging, even doing what seem like ordinary token social efforts may drain them a LOT.
I consider it a good sign, that he opened up enough to say he wanted to see you, but was too tired; in INTJ language, that's probably as close as you'll get to an apology or "consider this a raincheck on my time and attention" as you'll get from someone you don't yet know too well.
One thing, that is counterintuitive, which *might* help...and, again, depending on how well you know him, how long you've been dating, etc., would be to find a time you know he's at home, and drop by on fairly short notice with a spread of his favorite eats and/or drinks, and offer to just "be there" for him. It doesn't show, but INTJs have powerful Fi in their functional stack, and the combination of personal supportive presence + "no pressure" will likely make a big impression on him: if, he doesn't misread it as demanding or setting up an obligation.
Yes, I know, your post was whether or not he liked you, or was spending time on you, or really cared; but with the INTJ, sometimes you have to resort to ...well, I won't say *tricky*, but "feminine wiles" methods in order to unlock his shell and get him to allow you further in to what he is now regarding as his private space.
Come to think of it, though, INTJs are notorious for randomly disappearing and them roaring back, fully recharged. I wouldn't necessarily write him off just because he took a short hiatus from seeing you.
(A good gauge of how far you are with him, is whether he allows you to touch him, or has ever reached out to touch you.)
Good luck! With proper neglect, your INTJ will give you years of faithful service.