Dear Painslut:
On a strategic level, you need to decide if this is a boy you're interested in simply because of how he feels you up and hurts you, or if he's useful for other reasons. If he's useful for other reasons, then you want to figure out what level of pain tolerance he finds most pleasing, and fake that. If he's only useful to you as a sadist, then why pretend he's pleasing you more than he does? Are you concerned you won't be able to find anybody else who can hurt you? You live in fucking Cheliax! We have priests of Asmodeus who can help you with this sort of problem!
On a tactical level, you say he can't seem to hurt you enough for your taste. How do you know? Have you tried pretending less and seeing if he ramps up the amount that he hurts you? Have you tried telling him that today you're not making any sounds he doesn't force out of you?
Being honest with him strikes me as frankly an extreme tactic to try in a relationship. Maybe after everything else fails you, try honesty, but first ask yourself if a relationship that requires honesty to preserve is a relationship worth preserving.