Advice on how to get taken seriously by medical professionals

I've been going to doctors for multiple reasons for years, and I have the recurring issue of not being heard most of the time, it feels like a never ending battle of trying to know what's wrong with me, and why I'm in constant pain

At first I went with my parents cause I was a minor, and It got to a point where a doctor told me to "learn to live with it", without having a diagnosis or anything, I feel as if they didn't believe me

And now I'm in the same cycle cause a few years ago I stared having generalized chronic joint pain, and they send me from one place to another, and it's always "Well, with age it's normal to have joint pains and all that" ... I'm 19, and recently I called to be sent to a specialist, and my main doctor told me that she would, and when I went to the hospitals to claim for some tests I've already waited months for, I asked about this and they told me that the doctor sent it as a category that meant she wouldn't send me to the specialist, and she didn't even consider to tell me???

Sorry if it's a bit of a rant, but I'm a bit desperate, cause I don't have much experience fending for myself in this situations and have communication struggles (I'm autistic) so If anyone has advice I'd appreciate it