Sometimes keeping a symptom journal or diary can help your medical providers piece things together. They are only seeing you once for 10-30 minutes, but you’re living in your body and experiencing symptoms way more frequently. Don’t log obsessively, but maybe once a day review your pain (rated 1-5) and write down any noteworthy symptoms or episodes. And as someone else mentioned, get good at condensing your medical “story” to date, including your current symptoms.
Doctors will always go for the simplest explanation, even if it’s wrong. This is how they are trained (in the west, anyway). So don’t give up! Continue insisting on a proper diagnosis. Get another opinion. See a different specialist. If you find it difficult to advocate for yourself, imagine if this was your friend. How many mountains would move to get the same answers for a dear friend? And apply that logic and compassion to yourself. Have a bestie come with you to appointments if they are willing to.
A big part of the “suck” in this process is the not knowing. Will you be in pain forever? Will you get better? Will you get worse? Is it really a mystery illness? Will you ever get a diagnosis? With chronic pain you’ll find yourself exhausted often with the effort required to ignore the pain. So feel the pain sometimes. Lean into it. You may find it’s a relief to feel it instead of trying to block it out.
It’s maybe also worth accepting that these issues may never totally resolve. If they do, great. But what if they don’t? How can you live a happy and fulfilling life (which millions of people do with chronic pain/disability) even if it stays the same?
Lastly, I want to say that you have a separate problem, which is the lack of social support you are getting from your family. They are gaslighting you about your illness - of course you know your body best and are experiencing what you say you are. You are young and may depend on them financially, so that’s a needle you have to thread. But I’d encourage you to spend more time with friends who love and believe you.
If you have access, it’s worth working with a therapist on all of this. From what you’ve described, you have been left all alone to grapple with a disability that no one can even explain. That is an awful lot for someone to hold by themselves. Whatever happens with your illness, I hope you are able to get the love and support you deserve - which may never be offered by your family.