I am SO stuck with this chapter. Can I have some awkward help?

This book I'm writing has been going great, but it's a VERY dark book. I've had the notion of having a necrophiliac scene in it for a while, because it does hold symbolic relevance, but I've been at that spot for two weeks. I just keep going back in the book and adding more in the middle because I CAN'T get past this necrophiliac thing. I've never had sex, so I can't even begin to relate. I've tried to just make it up, but you can tell I'm just faking all of this knowledge. I was wondering if I put a few paragraphs leading up to this part, someone could help and say what would happen? Like what you would do (if the corpse was alive) haha. The idea is, this woman's baby died, and her husband just died. She doesn't want him to disappear like the baby did, so she wants to "become a part of him" through sex so he won't disappear. She doesn't think he's dead. She's gone insane and she thinks he's alive. She just wants to be with him. She used to be very attached to want to just forget the past, but at this point he's all she has left, as without him she has no future to focus on anymore. She can't let go of him. It's meant to be passionate and desperate.

“How they disappear.” I say to him. He nods a motionless nod.
“They disappear…They disappear…They disappear.”
I look at him and touch his face; his skin tickles my hand in its writhing grease.
“You won’t disappear, will you?” He shakes his head in a motionless shake.
“You need a shower; your skin feels like butter.” He doesn’t budge.
“I need to stay here with you, I never want to leave right here” he whispers through his lips which have been dried shut through crumbling paste, crumbling grins.
The sun picks at my face with a thread of gold, let in through the tiny rip of the curtain. I can feel a sleepy sun yawning on my cheek, and its pathway through the air examines the bobbing dust. Johns’ head sluggishly collapses to my shoulder, his neck bent and lazy as a rotting banana.
“Night time approaches” he whispers into my sleeve, his breath moistening and slithering above the barrier of my skin, writhing like fingers. “I was always alone.”
He says it with hopefulness, as if the aftertaste of sorrow lingers along his tongue determinably, until it knowingly reaches his loins.
“Do you remember when you were me? Do you remember when I was you?” I can hardly hear his muffled voice gnawing at my arm.
“When we were adjoined, and through that solitarily alone, and I would see me; I would see my transparent eyes, and you would see you; you would see your fading skin. We became each other, we consumed each other, and through that we saw truth; ourselves.”
The ghost of his palm crawls to mine, pulling my grasp to his. I wanted to be alone, truly alone, as him. Not alongside him. I lift his chin with great force stumbling along his slippery face and stare into his mossy eyes, revelling in the beauty of our loneliness.
“I won’t fade” I whisper, his breathless nose crushing mine.