Percy had never ever been touched there by anyone else. Ever. Being on the verge of release in his clothes, trousers and all, jarred him back to his senses. Or what was left of them.
When he tried pushing Oliver off this time, it was a little more forceful because he really didn't want to have a sticky, humiliating mess in his trousers because of just one more touch. It was just enough to get himself out from underneath Oliver and back on shaky legs that felt gelatinous.
"I need to go," Percy said abruptly and breathlessly before he fled the room.