Is he...

the only way u can know 4 sure is it u ask him. i know from experience how hard it is tryin to keep a relationship going when u hardly ever see each other, but the best thing to do is just talk to him about it. ask him casually why he seems so distant, or if theres something he would like to tell u...
i hope u sort things out and best of luck!
luv tanya... :D