I get this too! Daddy can get DTD twice a day for a month and I have one off week and it's been MONTHS since we been together lol. Even upto the very end of preg he was clawing at me hehe. Telling them the date of the last DTD and trying to relate it to something they may have felt at one point can help them put things in perspective. I told Daddy even though I didn't look pregnant I felt as tired as when I had Glandular Fever and like I had a constant hang over, as Daddy got GF when he was young really bad for months he understood moreso because I didn't "look" pregnant so he didn't understand what was the problem. I think they take it to heart, they think it's them, not the pregnancy or other situations and they begin to doubt themselves and use sex as a way of reaffirming that we do love them and want them if that makes sense..