starting over, it could just be that your son needs some mental and emotional space to deal with the break up. The "buffer" could be there because your son is afraid to become emotional in front of you..the buffer would keep things more casual, less intense. Have the two of you had a good, long talk about the divorce and how you each feel about it? Maybe he's in love with someone and is fighting it because he sees the hurt that come from it. I've never had kids go off to college but the other women could probably tell you that the kids are torn between the excitement of becoming independent and the fear of becoming independent.
I don't think you will lose your son. He may just pull away for awhile. Let him know that you are always there for him, when he's ready to "come back".
Give him a hug and here's one for you (((HUG)))