How to tell my boyfriend that he makes me feel lonely?

I've been with him since December and we usually meet on the weekends. We used to communicate a lot. We met on OkCupid and at first we wrote to each other almost every night, we eventually started going out. During winter holidays we didn't see each other, because we were 300km apart and that's when he started writing to me less. I accepted that we're together a month as and we don't really have that much to tell each other and that he was actually busy, had some family drama and so on.

When we're together, he's wonderful. When we're apart I don't exist. I always promise myself not to write to him until he writes to me and I always break it after a few days. And then I get one reply from him after many hours and silence afterwards again.

I want to know if he actually cares about me or if it's just the regular sex hd wants from me. I know he's busy. His family drama got a bit complicated again, but is it so hard to write something?

When we parted last time he said he'll probably be busy, but that we will write to each other. I don't know if three messages since Sunday (each one on a different day) actually count as writing to each other for him, but it doesn't count for me.

I want him to know that I want to actually exchange a few messages at least once during the week, but I don't know how to tell him, when he never really replies. And we'll probably not see each other this weekend, because he's busy. I had a nice date planned for wednesday to remind him that I'm more than his booty call, but I don't know if he'll have time at all. I only asked him 21 hours ago if he could get some time on Wednesday, so I'm still waiting for his reply...

I feel like the songs "Information" and "What good could ever come of this" by Eliot Sumner

UPDATE

I actually got a reply and he has his points, but I won't just leave it without letting him know how I feel. Hopefully he'll take it heart and will actually answer me tomorrow in more reasonable time.

UPDATE

I decided to give him a chance. He had been really busy and exhausted. He knows his response time was terrible and he most likely even figured out what makes me angry with him. Hopefully it'll get better now. He came to me last night knowing that he'll arrive late and exhausted and will have to leave again early in the morning and that I might not be in the mood to give him any, but he came anyway to prove to me that he cares. At least he's not completely stupid