the untold story

I saw a ghost in our apartment.

It sounds like I'm lying but I promise on my life I'm not. This really happened to me.
When you get to the end of my story, come back up and read the previous sentence because I know you're gonna doubt me.

I saw him last spring. It was early morning, when it's still dark outside and no one's awake.
I woke up suddenly, knowing something was wrong. I turned to Corey's side of the bed and he wasn't there. So I look on up the wall, away from the bed onto the bathroom door where I see him in his white undershirt and shorts and I watch him slowly shut the bathroom door behind him.
I think "Oh no, Corey's up sick."
I roll back over on my side and try to go back to sleep to no avail; I'm too worried about Corey.
A few minutes later, I feel his side of the bed go down and I know he's came back to bed. So I turn over and ask "Are you okay?" He takes a second and says, "...Yeah, why?" "I saw you go in the bathroom and I thought you might be sick."
"I didn't go to the bathroom, I've been here sleeping."

I couldn't sleep the remainder of the night.

Who was that walking into the bathroom? And who did I feel crawl back into bed?