He's probably feeling insecure that you may move on from him when you start college. Boys suck at saying what they feel sometimes. Good on him though for not being a "douche" and trying to hold you back.
Why has my boyfriend been acting strange since I told him I registered for college? He congratulated me and everything he just seems a bit skittish for some reason.
A huge change is being thrown at him and he knows that this move will alter everything in his world. He doesn't know how what is happening for you will impact him and his future and his relationship with you.
Encourage him to get into a training program or apprenticeship or something like that.