Don't Move.

Shh

“Shh,” Not again. Hot weight pressing down, soaking through the sheets. “Don't move, can’t let them see you.” A quiet hand shifting over sleep-swollen lips, soft and rough with calluses and slick with sweat, shaking in fear.

In the morning, I find him sitting at the top of the stairs, arms poised as if holding a gun, back straight. Keeping watch.
“Don’t move, let me go first.” He rises to a crouch, just below the line of the banister, slinking down the stairs to make sure the coast is clear. Eyes gone, head gone, he’s still in his pajamas, but they are starting to feel more like a uniform than his desert camouflage. His hand swoops up to wave me forward into the kitchen. My sleepwear isn’t enough to keep the chill from reaching me, and even as I pass Tristan I don’t feel warm. I feel sad. Like there’s mud in my throat.
“What do you want for breakfast, Tris?” I ask quietly, afraid to startle him. Even his pantomimed gun is solid in his fear.

Friends have stopped coming over, stopped checking on us.

He’s on medications, he has hours of therapy every day, but it seems like every day is worse than the one before, like the more he’s home, the more he’s not.

“I’m sorry,” Tristan whispers, coming up and hugging me from behind. I took the day off work because he had an intense flashback this morning and I couldn’t leave him home alone. With his lips on my neck, stubble brushing my skin like sandpaper, things feel like they used to. Like The Before. But I can feel his bony arms around my waist, and Before, they were muscled and strong, and he was the one supporting me. “I wish I could stop… I wish it would stop.”
His words are wet, but I know he’s okay because tears only come in lucid moments. I drop the dishes I was washing into the sink and slowly put my dripping hands to his forearms, finding the warped bullet scar just below his elbow. The water runs and drips to the floor over our hands as I pull his shaking fingers to my mouth and kiss them. And he turns me in his arms, and we finally move together for the first time since the day he got home. He’s skinny, I do most of the work, whispering “Look at me,” when his eyes start to drift and I can feel his body seizing up with a memory. My hands don’t leave his face, forcing him to look into my eyes, forcing him to stay here. You started this, you bastard. Don’t leave before you get to finish it. At the peak, we’re crying from sorrow and change and bliss and love, and when we fall to the sheets afterward, he whispers, “This is a war,” and I don’t even need to ask him what he’s talking about, because he holds me too tight and I will have bruises along my spine in the morning. “And I am going to lose.”

I wake to a soft, strong, callused hand over my mouth, and a hush. Don’t move.

This is a war. And everyone is losing.
♠ ♠ ♠
So, PTSD is a beast and it ruins lives.
I'll leave the rest of the story up to you, because there are a lot of options for where it came from and where it can go.