Why does autism exist?

I hate having autism, add, ADHD, and biploar disorders, I feel I can't live a normal life such as getting married, having kids, driving, getting a high paying career, serve the military and all that awesome stuff, I feel my life is worthless and no use of living, I have a hard time trying to find people to hang with a friends, a relationship with a girl and a hard time focusing on my education, I feel autistic people can't do anything that normal people can do, I feel Autistics are not accepted anywhere and we're not treated like everyone else, why does this diasease have to exist, if there is a god then he is the biggest prick for this, and I feel that people with mental disabilities have no reason to live, I feel that I just want to blow my autistic brain off, what do you think? Is being autistic worth living?