Basic Training Blues

My boyfriend of 2 years is in Basic Training for the Army right now. I write him every single day and update him on what has been happening, tell him I love him and I'm proud of him, send him jokes, etc, and I've only received one letter from him. His mom has received 5+, and while she wouldn't rub it in my face, I think she assumes I have gotten as many also, when I haven't. Why is he not sending me letters? Could he have changed his mind about us? Is he too busy? And if so then why is he writing her and not me? I probably sound really selfish and childish right now but I just want to know why I'm not hearing from the man I love.