How to tell my girlfriend that I want to be her slave?

Your right that kinda creepy if you just gonna say "I want to be your slave" lol I think the best way to tell her is by saying ----> I really wanna be by your side and wuld even be your slave to show you how much you love her and want to do everything you can to make her smile and entertain her. Lol I hope this help :-P