When in doubt - ask him or point out to him your observation and let him share the reasons.
The speculations can be many. If you meant close (by intimately close) then he probably wants the best of both worlds- intimacy when you're in the same area and freedom to explore other options when he's elsewhere.
It sounds as though you're the one thinking about him as you said "He's in my mind many of times during the day" and that he makes you miss him. Your feelings result from your thinking (since no one can make another feel something )
Just ask him or write him an email to share your troughs and feelings on this issue.
The only way to figure out how someone feels is to ask them directly. Of course, if he is confused or does not want to share, there is not much you can do to get that info out.
If you believe there is little chance, he probably feels that way too and don't' want you and him to get hurt. That is understandable. At least you could remain friends through a distance relationship and come to terms with that so the two of you can move on and be happy.