He SHOULD hate you, you dumb bitch. You put his relationship in jeopardy just for your selfish cock lust. You didn't know your boyfriend would be into it, and you didn't know dickboy's girlfriend would be too fuckin shy to be angry about it. You want to swap? That's cool. Do it like a grown up would and sit everybody down for lunch at Denny's like the rest of the swingers do.
Fat chick is hotter anyway.