How do I get my long distance boyfriend to call me more often and be more affectionate?

basically when we're together, my bf is the sweetest most attentive guy around, but when we're apart, he barely acknowledges me. we live in different states for college and we've been dating for 4 months. he says he wants to marry me and has made somewhat fluid plans to move to be with me. i told him that only talking to him once a day felt a little too casual and that learning to not care if he called was weird. he said that casual was good and that he's just really busy. now i'm worried that not caring if he calls and only talking once a day will diminish my feelings for him or make it weird when we do see each other b/c we barely talk. i've tried everything to get him to call me more often and he's convinced me that i just call too much. i know he's not cheating, but i just wish he was a little more attentive and affectionate for the weeks we're apart. how do i get him to talk to me?!?!?!