Oh, honey. You are so young to be dealing with all of this, I wish I could give you a hug. I don't know if it helps, but what you guys are going through is so normal. Not to say that it is ok, but if it makes you feel any better, almost everyone with young kids feels like their marriages are not in great shape a lot of the time. There have been numerous studies showing that marriage satisfaction dips tremendously with the arrival of babies. That is not to say that it is going to be that way forever, but just that it is a totally normal place to be right now.
As someone who had PPD, I can sympathize with both of you. Antidepressants are a wonderful thing, but they have their side effects for sure. The only thing is, I can't believe that his doctors are giving them to him without insisting on some counseling too. He needs to have someone to talk to about the PTSD. To the best of your ability, encourage him to do that.
I agree with the other moms that you needs to get some counseling. You are in a very tough position, without a lot of life experience, and need some help dealing with it all. If the VA won't help you, find someone privately to do it. Be open about it with your husband, but not pushy. Just say you need some help dealing with all of this and you are going to get it. Maybe it will set a good example for him. Even if it doesn't it will be good for you. your therapist will help you figure out what you want to do next-- maybe you want to go back to school, get a job, start a business at home, whatever. While there is nothing wrong with wanting an affectionate, committed partner (of course), you can't expect a man (or anyone else) to make you happy. You're young and have lots of time to figure this out. But get yourself some help to deal with this challenging situation.
All the best to you and your family!