While you're fucking her, tell her how hot it would be to see her with another man's penis inside of her. Tell her this often during sex so that it will excite her. We know that you want this. You think about another man fucking her often and it's time to make this a reality. Get her to post an online ad with you. Be honest and tell her it would be hot to see her with a guy with a really big dick. You want to watch a guy with a really big dick take your girl as if he were her girl. Make all the arrangements to make this happen. Invite him over and allow him to fuck her as you take out your little dick and stroke it as he pounds your girl and makes her moan more than you ever have. When he is finished with her you will have a little penis with cum on you and you will not be able to get your little dick hard enough to put inside of her. This will add to the humiliation you desire from her.