It's hard for him to trust by now, but as much as he wants to keep his guard up for his own safety, at heart he is just the kind child he's always been. So, when you'd first met, he was skeptical for perhaps a few moments before trusting that you, similar to him, had a gentle and trustworthy nature.
This time, though, for perhaps the first time in his life, he was right. You'd grown impossibly close. There was nobody in the world he could trust other than you, which made him particularly.. clingy.
As he sleeps next to you, almost drowning amongst the blankets, his body twitches. His breath quickens and he reaches out a desperate hand, trying to find you. As the nightmare becomes more realistic, twisting into ever present memories of the past, his mumbles become louder.