I have no written evidence!

Hi guys, so I have a rare condition (which is pretty unheard of). However, my consultant which has no ‘referred’ me on has written no notes on my condition and just the diagnosis in my medical records. Is just a diagnosis enough? I have mental health diagnosis’ aswell which again, I have no physical proof (letters for example) of.. I’m only 17 and not far into my treatment plan so just wondering what I could do to back my claim up? Thanks in advance! ☺️💕