It Hurts So Good has been a big UK hit for Susan Cadogan and Jimmy Somerville; in the US Millie Jackson took it to number 3 in the soul charts; the best version by far is Katie Love and the Four Shades of Black’s 1971 original.
There are three possible interpretations of the lyrics:
•It sits in the boyfriend-worshipping tradition of He Hit Me (And It Felt Like A Kiss);
•It’s about anal sex (this point was popular in the music press at the time of Jimmy Somerville’s cover – no prizes for guessing why the hacks favoured that view);
and, most plausibly in my opinion,
•Like Son Of A Preacher Man, it’s a woman’s hymn to the pleasure and pain of sex with a well-endowed man.
By contrast to the a-side’s deep soul, Don’t Let It Go To Your Head on the b-side is the sort of scorching funk-pop that’s more readily associated with the hits of Honey Cone or Jackson 5 than Muscle Shoals' southern sound where it was recorded.
NB I’ve read a few accounts that claim Susie Rainey originally recorded It Hurts So Good as Hurt So Good, but it’s a completely different song. Unless anyone knows better…