How do I say this?

My boyfriend and I have been together for a year and have been long distance for 5 months. When we're together he's so loving and considerate. However when we're apart, I don't feel like he really cares about me that much. I know he does and I know I mean a lot to him but I don't feel like he treats me as nicely as he could, he barely texts me, I always have to ask him to talk on the phone, I'm the one who has to make the effort to communicate. He's apologized a few times before and said "I'm sorry I don't treat you as well as you deserve". I agree with him but what am I supposed to say to that other than tell him he does? I love him a lot and I don't want to break up with him, I just want some validation that he cares about me even when we're not together in person. How do I say this to him?