How do I get my diagnosis in writing?

I am a adult male 36yrs old I was only diagnosed back in 2010 with Asperger's syndrome, my GP sent me for assessment with a district physchiatric nurse I think it was I forget, I never had this in writing I was wondering if and how I get that confirmation in writing? I also have suspected dyspraxia which my gp said once it may well be the case as it often is present in autistic people, I can't remember if I had anything in writing or should I have had, or do I need to request that? As when mum helps me filling out ESA forms I keep thinking I should surely have this in writing to accompany my assessment for work forms, when explaining my difficulties and inability to function in relation to work, my GP always signs a limited or inability to work sick note 3 monthly I am confused how or what I need to do to prove my diagnosis?

I have major issues sleeping and waking up I cannot remember anything two seconds after being told, I could not operate machines on JSA before I forgot to pull the tool down on a diesel press twice which could have killed people, I fear that if they try to make me do JSA work I'll be endangering my self and others forgetting basic safety and operation of machines etc, not only that I'd never get up or sleep I'd be fired for lateness in a week?

I'm certainly not stupid, but it takes a baby learning hand shown teaching repeated over and over for me to understand things, not everything I remember but sometimes this baby teaching method may work but rarely, I rely on my mum way to much to explain things for me and help me, I am just really worried this recent capability for work assessment form for ESA, is maybe going to put me in a position of homelessness or vulnerability, and there doesn't seem to be an understanding of my traits or any written diagnosis paperwork to accompany it although I was formally diagnosed in 2010?

Was I supposed to or can I request my diagnosis to be written on paper, or have I forgotten if they did send this maybe or thrown it away not thinking clearly at some time as I wouldn't put it past me to not understand it if I was sent it by mail and throw it away???