My GF's gone through the same windmill, over the span of seven (or more) years before finally getting a diagnosis. Multiple ones actually.
Her abdominal pain issues and discomfort were blamed on period pains first, then IBS (because her mother has that too), until finally, after she herself asked for it, she was diagnosed with endometriosis (and an ultrasound revealed a 10cm cyst).
Likewise, she's struggled with being punished for being a naughty child during her upbringing, school problems, and later depression and suicidal tendencies when put on medication for either depression or birth control. It was only once her son was diagnosed with ADHD that she recognised those symptoms and got herself a similar diagnosis. Both are on proper medication for that now and it's a huge improvement for both.
TL;DR there's still a lot of ailments that aren't easy to diagnose.
Your girlfriend also made the "mistake" of being a woman, and I wish I were kidding about that.
The fact that "borderline histrionic" is diagnosed much more often in women echoes back to the Victorian diagnosis of "hysteria", and pain reported by women is often discounted.
And unfortunately for her, ADHD also falls into the category of doctors ignoring women. It's slowly getting better, but essentially, all diagnostic tools were tailored to boys, and the first studies for girls' symptoms were beginning to come out in the early 2000s.[1] If you read that article, you'll also find that her way to discover ADHD is common for women - you find out because your child is diagnosed.
It's not only that ailments are hard to diagnose, it's that most medical research is tailored towards white males. (And most experiments are geared towards the college age group, due to ready availability).
The further you're outside of that group, the more work you'll have to do on your own.
Her abdominal pain issues and discomfort were blamed on period pains first, then IBS (because her mother has that too), until finally, after she herself asked for it, she was diagnosed with endometriosis (and an ultrasound revealed a 10cm cyst).
Likewise, she's struggled with being punished for being a naughty child during her upbringing, school problems, and later depression and suicidal tendencies when put on medication for either depression or birth control. It was only once her son was diagnosed with ADHD that she recognised those symptoms and got herself a similar diagnosis. Both are on proper medication for that now and it's a huge improvement for both.
TL;DR there's still a lot of ailments that aren't easy to diagnose.