Hi Rachel -

What you're experiencing is not uncommon, I'm sure you know that at this point. I have an understanding spouse as well, but he's still a normal man who has normal desires, and I also feel guilty when the 'drive' is just not there for me. After 14 years of marriage, the one thing that's key is communication.
If you haven't already, talk. Ask him how he feels about it. Let HIM talk, and let him get things off his chest as it were. Be prepared to hear things that may 'sting'; but it's important as a couple to make sure he feels you're there for him too. Sometimes we get wrapped up in the PTSD thing and the 'healthy' partner may start to resent the syndrome (not you). If you are up to it, tell him you want him to share with you what it feels like for him, and then be prepared to just listen. Sometimes the intimacy issue isn't as much physical as we think. Then again, sometimes just taking a shower together and using lots of soap can work wonders too, it's what works for the both of you.
Good Luck...