Here recently I've been telling my bf how much I want a bigger cock than his. I tell him what I would want a bigger cock to do to me, and how I would do anything that the guy with a bigger cock told me to do. While I tell him this, I usually use my dildo to get myself off imagining it being a different guy's big cock, and my bf jerks himself off.
I tell him all the dirty things I would do to a huge cock. I tell him I would have no limits and do things for a guy with a big dick that I'd never do for him. It drives him wild and gets him so horny heheh. I tell him how I would make him watch me get fucked, that he would have to clean my pussy up after, and that I wouldn't even be able to feel him inside of me after. I love to tease him about how much better a big cock would feel, and how much better a bigger cock could fuck me.