Look at the positives... she came back to you for sex which means that you've presented yourself as a safe person, even if it's early and there's a lot of work to do. After my wife and I were intimate yesterday I did have to fight off many thoughts but I acted as if nothing happened and went back to DB mode. Low and behold, it happened again this morning.
It's tough but just remind yourself that what you've done so far seems to be working and just keep plugging away at the same level, nothing more, nothing less, until something stops working. Act as if, have no expectations and be you.
Me: 31, W: 29 T: 4 M: 2 Kids: 3 (SS: 7, SD: 4, D: 3) Separated, still living together: Nov 2013 Separate bedrooms: Feb 2014 W working away; kids with me: Nov 2014