Should I tell him? (Military experience wanted)

Would you tell someone who was *just a hook up* that you're now expecting? 
I hooked up with a newly divorced/separated army guy in Fayetteville since May. I've been terrified to tell him, due to his mental situation of dealing with PTSD from Afghanistan and still working 24 hour shifts on base (props to everyone that does this). 
One night he took his Lunesta for sleep, woke up and (to me) seemed viable. I later found out he had no memory of it. We had sex and he was saying his fantasy of getting me pregnant and having his baby, he asked me "tell me you want me to get you pregnant", I did, and I'm sure that is the night we conceived because I was ovulating, and I told him earlier that day the first time we had sex that day/night. 
He disappeared for a while, he didn't even log onto Tinder for over a week. He said he just was disinterested in sex and talking to anybody. 
He became active again, and actively talking to me again. He is into extreme sexual adventures that I had doubts I could provide for him, so I assume he found someone else. I also tested positive for Chalmydia after hooking up with him a few times after two visits to Fayetteville/Cameron.
Mid-sexual conversation today, he drops how I'm "too attached", and he is "getting out of the army and moving back to California on the 20th". I've never heard of such a quick release, but okay. He said our fling was over and he didn't want to see me again. All of this after an hour of talking about how he wants me to do one of his fantasies to him, as we have been since April/may. 
He has two sons already, and (by what he told me a few months ago) his (ex) wife took the kids back to Sacramento where they are from. I knew our fling was just a hook up, I knew I -should- have protected myself for more reasons than one.....
But I am terrified.... I am terrified of the small things he has been open about to me. Since we were just as a hookup, I didn't ask much about his mental state. I let him talk when he wanted to express things to me. I am scared to death of what would happen if I tell him I'm pregnant.... I've told my friends I don't even want to tell him, and everyone brings up morals and ethics, and how it isn't right to never tell him of another child, and "if I had a child out there I would want to know".
I just don't want him to be so stressed and angry that he would commit suicide, seeing as he has PTSD and is already dealing with a divorce and has two young sons already, all the way in California. Unless his mid-conversation "I'm done with you" was because the ex wife is coming back. 
What should I do? I can live life without him, but are my friends right? Is it wrong to never tell him about this??? 
*******EDIT TO ADD: the first thing he said was, he is from California and said he was temporary, but we were in an emotional surrogacy if you will. He missed treating a woman and having a woman around (I assume this is where the Lunesta induced "let me get you pregnant" came from) and we acted like a relationship, but knew it wasn't on these terms. I know he will leave Fayetteville one day, but it kinda hurts how I've been carefully planning to see how to tell him I'm pregnant--- when today he just drops (mid sexting) "you're too attached, we're done" out of NO WHERE. When I say I want NOTHING to do with him, I mean that. I don't want him to know, I don't want him getting comfy little updates in California, nothing.