Honestly, I like it the way you originally phrased it best: "If you keep looking at me like you want me, I'll have sex with you again right now." It's direct, no cheesy innuendos. I would maybe shorten it to "If you keep looking at me like that, I'll have sex with you again right now." Or "Keep looking at me like that, and I'll fuck your brains out," depending on how crude the character is LOL.