This may be more common with women patients, but my father, over his life, had doctors tell him all of the following were stress and nothing physical wrong (all subsequently found to be the named condition):
Stomach ulcer
Glaucoma
Heart attack
Stomach cancer.
I also had a very severe burn, which nurses decided wasn't serious enough to bother a doctor over (but ended up being moved to a specialist burns unit once one saw it later...).
I think doctors belive they can gauge how bad something is with their spidey senses, rather than the words you say, and perhaps if you're not screaming, they think it can't be that bad. They forget we're british, with stiff upper lips :-D.
With the burn, they did ask me why I had tears running down my face, but I can only think that because I wasn't wailing, they didn't understand it was a response I couldn't prevent, to great pain!