I watched a horror films years back about a story writer or I think he was a journalist... anyway so he goes through this tunnel and at the end of it he ends up in a sick twisted world e.g like a woman doing the crab walk in the exorcist but I don't know what the film was called :(. Does anyone know? I reckon its prob an 80s or early 90s horror film...

(I know this thread is old, I just saw it today.. )The crab walk scene totally sounds like something from the movie In The Mouth Of Madness... I can't seem to find the scene to show you... but your description is close enough that I would think this is the movie you're looking for
In the Mouth of Madness (1994) - IMDb