My current GF cums hardest when we're in a threesome, and not so much when just the two of us. She says it's because she likes to be ravaged by two cocks with me in her asshole (my favorite). It's great sex for me too, and I love how much she gets off on it, even though it takes someone else's penis. However, I do wonder if it's because she prefers the feel of a different cock in her pussy (noting the best results are with guys with bigger cocks). I'm not complaining but it would be great to think it wasn't because she was dissatisfied with my penis. Any thoughts from any GFs who also love DP?