Speak to Citizens Advice about getting help with the assessment for Disability, you may be allowed to bring someone with you.

I’m looking for people in similar experiences as me, I’m young and still trying to get a diagnosis so if you want to talk feel free to message me! I know that it can help to vent sometimes.

Prepare a written sheet of EVERYTHING you may need, so you don't have to remember anything. Have a list of everything- from your date of birth, bank account info, diagnoses & how long you've had them, all your doctors contact info, things you can or can't do on your own, etc. I don't know if you are in the US or another country, but here I can Google "applying for disability checklist" and images with a checklist of necessary info comes up! Have a section in your notes of the answers for all listed questions written down, and you'll be set