It was just as hard on me when DD oldest was taken off to school in'91 100 miles away. Then 3 yrs later DS, but 500 miles away.I cried both times. I missed each so very much and still do when they are home for a visit and leave again. It is just something each person has to work through. They also are missing you even if they pretend not too. DD told me a few years ago, that she was so homesick at first, she almost came home. She was living in a trailer in one of her grandmothers' yard, but she said Mom it just wasn't like being at home.DS gave us just enough time to make it home and called - "just to see if yall got home o.k." but I could tell in his voice, he was really homesick.
Just keep busy and keep sending him letters, cards and nothing really mushy, care packages etc., but just something to let him know you still think about him.
Please DON'T change his room out right away, because when he does come home, he won't feel like he's home if his room is changed into something else, he'll let you know when he's ready for that. I know from experience!!