Maybe the stress of TTC and your other pregnancy problems have helped to make DH a little wary and uncomfortable, and you need to get the "spark" back? Instead of focusing on DTD, just try spending time together and being with each other in a loving way without the pressure of DTD hanging over your head. Then if you are both relaxed and calm and not under any pressure, DH might be more inclined to feel the urge to get jiggy with it.