IIN for my BF to react like this?

If he acted like that, I'd say there has probably been some abuse in his past. Watch out for unexplained bruises or if he becomes really withdrawn, talk to him. Don't dive in and ask him if someones abusing him, just tell him that you'll be there for him and he can tell you anything. You can't make him open up, but you can make it easier for him to do it on his own.