Maybe you SHOULD have an MRI done on the cervical spine, since you have DDD. I've got it "up there" too, and that's how the darn herniated occurred. Perhaps you have something going on up there too.
Like I said, the collar really helps me. You can get them at the pharmacy or medical supply store, and they aren't very expensive. They make MY headaches go away quickly. It's worth a try. I hope your doc can help you. God bless. Let us know what he says, ok? Hugs, Lee