As the sensation of warm cum inside the condom caresses your skin, that starts to arouse you, and your cock hardens once more, pushing the glans into the pool of lukewarm jism. Sliding the cum-slick condom back and forth on your cock only makes you harder.
Now you're ready to fuck him again. Slap his ass, wake him up, and roll him over. If he's a real slut, have him pull the condom off and clean your cock with his mouth before you use his hole once more.