I started having lots of pains in my back and some joints specifically the sacroiliac joint when I was young (at 11yo) and went to about 15 doctors, the first 14 told me that I was either faking it or it was just growing pains.

I went to a physical therapist literally told me within 10 minutes of looking at me and asking me questions "I know exactly what you have but since I am a physical therapist only I can't diagnose it, go to [doctor that I already went to and told me it was growing pains] and tell him to make you these tests"

Turns out I had ankylosing spondylitis (a type of arthritis) but since I was 11yo nobody wanted to actually look into it because they thought I was just growing or faking it.