TTC and PTSD?!

My bf and I are ttc, but I'm very frustrated because he hardly ever wants to have sex, including during my most fertile days. He is a veteran and has severe ptsd and he has quit drinking to be a better dad when our little one comes, but not drinking has killed his sex drive. We have discussed other ways for him to cope that might help, but we keep coming up empty handed. I've tried so many things to be sweet and try to connect with him but it always seems to backfire. I want to come up with sensitive ways to connect with him and also get him the mood to attempt making a baby. It seems ironic to me that the struggle is to be a better dad, but we can't make that happen if we don't have a baby. And month to month I'm struggling with the waiting game and just keep getting negative tests. None of my friends are in the same boat and I'm feeling isolated and alone with no one to talk to about it. Does anyone else struggle with this with their SO? My heart breaks for him and the pain he's in and I just want to feel intimate and connected again. Any and all advice is so appreciated.