How do I get a autism Assessment?

Hi, I am 23 and I have asked my GP for a assessment for autism or additional needs assessment, the GP gave me a number for a website called we can I telephoned them and they said they dont know why the GP referred me to them as they cannot help, they suggested I contact the local authority which I did online but the services are for children up to 18 years old. I am unemplyed as I struggle to hold a job as I have no self esteem, Im on medication for depression and my doctor just says Im lazy but I cannot change doctors as there isnt another one. I self harm and attempted suicide in the passed however my good friend who has become my voluntry carer for me and a trained mental health first aider, talked me out of it. I cannot talk on the telephone, I dont open mail, I struggle to hear more than one instruction at a time, I have no money as I cant claim ESA as they said I havent been assessed even though my friend came with me and spoke on my behalf, I cannot understand job seekers and to be honest feel like giving up! please can someone show me a way of been assessed as an adult, when I was born I died due to lack of oxygen but was revived and my parents were told I would have problems in adulthood, Im confused,sorry to ask so much but I need to know whats wrong with me.