Just tell him.
Hon, the nerves wired weird after the twins. When you touch my breasts I feel like throwing up. Maybe it will go away, but for now? It's like taking a cold shower. Can we just get some pretty lingerie and lock the girls away for awhile? I really don't want to throw up on you.
(or sub nausea for whatever you're feeling.. See below)
Nerves rewriting after nursing is common. Some get more sensitive (direct line to god), some less (um, my nose feels sexier when stroked), some wire to a kind of nauseous feeling (pardon me while I puke), some trigger needing to pee (accident 'need'), some become painful (whaddaya think you're DOING???). The weird wiring is fairly rare (nausea, peeing, pain), but it does happen. Most commonly, women lose sensation (part of why breast lifts are common. When you have a direct line to god, ya don't wanna mess with that!).