Work in medicine, and you'll find a lot of malingerers. Some of them don't even realise that they're faking it. Yes, it sucks from your point of view that no-one believes you, but from the other side, a lot of people fake it, and you have to sort out what's actually going on.
https://en.wikipedia.org/wiki/Munchausen_syndrome
https://en.wikipedia.org/wiki/Munchausen_syndrome_by_proxy
I used to be a neuro tech and have done a lot of EEGs in my time. There are enough people faking seizures to make it a non-trivial issue. Munchausen-by-proxy is a particularly sad problem, where parents make their kids sick in order to get some attention or compassion from others.