Why does my boyfriend hold on to the back of my neck while we walk is this a sign of control?

This is a sign to his psycho that he has found his mate and has a close relationship also a sign that others keep away from you as you are not resisting the same and hence denotes others that you are too happy with him. Basically it is a combination of fear (to loss you and hence hold on to the back of your neck to show publically that even if i forget thou should not) and comfort (to satisfy his psycho).