Umm... If my opinion in the matter counts, I feel like the sex scenes are good to be there, just because that's what their relationship is like, I think. It started out as mainly physical, the sex is a big part of it. Of course you don't have to write down every single time they have sex, so don't go pushing a scene into every single chapter :D In moderation, though, I think they're good. You write them well, I enjoy that. I think the pace you've now is okay. Yeah... That's what I think. If anyone cares...
But when it comes down to it, it's a matter of taste. It's your story, you say the last word.