He didn't think arguing about who was really the lucky one here would have been all that useful at that precise moment. For one thing, Hermione seemed to be just as enamored of him as he was of her (for some strange reason), so he would have likely been wasting his breath. And for another, he really didn't have all that much breath to spare, at the moment. Even if he wasn't moving especially fast, he was terribly excited by now, to the point that he could barely kiss her for more than a few seconds without gasping for air.
In the end, he simply gave up the battle of trying, in favor of leaning his forehead against hers or raising his head just enough to watch her face, with the occasional brief kiss and halted, "I love you," in between groans. And an open-mouthed smile when she reached up to push his hair back, so that she could see his face. Or perhaps it had just been tickling hers, but somehow he suspected it was the former.
But he couldn't keep any of that up for long, as his eyes started to roll. He wasn't going to last much longer. Of course, he hadn't even expected her to come the one time, so hoping to get her off twice before he came was probably terribly ambitious, even for him. On the other hand, he'd had much more destructive ambitions in the past. As far as these things went, the wish to drive his girlfriend mad with pleasure was relatively mild, by comparison.