My son wanted to change the position with me.
"I want to sleep here." He said.
"It's Okay. Becareful not to fall out the bed. I sleep in middle. You sleep in outside. Mummy sleeps in inside."
(Beside my wife is a wall. So I let him know it was inside.)
I am a bit confuse the preposition for the people in the bed.
What adjective should I use?