Feeling Betrayed by My Own Body

In 2017 I was diagnosed with Functional Neurological Disorder. It came on all of a sudden and I had verbal stuttering and body tremors/ticks, migrains (for the first time), and lost the ability to control my arm and leg movement. I was put into a wheelchair, and then contracted costochondritis. You might look up FND, there are a variety of different symptoms. No cure, but I am walking and talking again after a ton of PT and OT and Counterstrain fascial massage.

I've been told by several doctors that I have an auto immune disease but they don't know what it is and when I ask if there are any tests to help pinpoint which one it is they all just say that they aren't a specialist but then won't give me a referral for a specialist and it's been about 3 years of this and so many doctors. Also since I just turned 18 this year I'm also told that "I'm too young to actually be experiencing this much pain" and that I'm just "over exaggerating" and not just by doctor's but also friends, family, including my sister and my step dad especially. I have arthritis, costochondritis, tendonitis in my elbows and ankles especially, frequent migraines, and verbal as well as motor tics that no one can explain to me. No one else in my family experiences tics of any form and no one I talk to has any answers about anything. I'm constantly feeling sick and I don't know why.