huh, this is a tricky one.
I assume you want to be the pet/child, and you want to be manhandled and abused and debased by your girlfriend. You're quite the glutton for punishment! (Assuming you're on the receiving end of this.)
I interpret that as stemming from a fear of adulthood/autonomy. You want someone to be in charge of you, to spare you from having to appear collected and in charge. But at the same time, you know you're an adult, so you need some reason for your girlfriend to be holding your leash, so you engage in the humiliation/domination side of things to play along as if you're not CAPABLE of doing your own thing.
I could be way off. This one I don't understand as well as the previous ones.