I've not been there, done that or gotten that t-shirt...my oldest just started her junior year at a private college and lives at home. She's looking forward to moving out the day after she graduates. I figure I'm paying for her education (which in the long run will cost more than a very nice new home), she can pay for her dwelling, if it's not at home. So, here she stays...
However, I can hear how sad and affected by his leaving you are. First off, you've raised an intelligent boy. Not only that, but you have taught him right from wrong against all odds. Good for you and him. What a smart young man he must be, honors!
Slowly you will return to a new normal. Baby steps. If you communicate with him, you will still be in his life, even though he's not at home.