Autism - How do we diagnose if an adult child has it?

I hope my blogger community may have some suggestions. I have an adult child that I fear may be borderline autistic or have something called "Asperger's Syndrome". However, I don't know how to find out. I mean he's an adult, and he's no longer covered by my insurance, so how can I force tests? I feel foolish that I didn't suspect this when he was a child - I knew he had ADHD, depression, and some emotional problems - but not autism in any form. His second last week in high school, his counselor told me she thought he was borderline autistic - in response to a comment I made - something like "I said something to D (changed the initial to protect the innocent) a couple months ago and at the time he didn't respond, but then yesterday, he repeated it back almost word for word." Supposedly, that's a clue? A couple of my friends have mentioned their concern about D, too. We looked around some online, but I found nothing conclusive. One of my doctors said he'd look into it for me and hopefully have some helpful answers for me when I see him again this week. I've run into a couple blogs this week speaking about autism. I'll have to find those again and read those closer. It's not that my adult son is unhappy. He seems fairly happy, but he's 26, living at home, working only a part-time job and seems too happy living out in the garage (his makeshift apartment) playing video games for most of his life, and I don't see him dating or mingling much with people his age. He's not driving, either. His work is within walking and biking distance. Also, although he took a computer repair class and got his A+ certificate, he's bagging groceries, chasing carts, and cleaning the store. My hubby says he was unlucky that 911 happened just a couple months after he graduated and that it caused the computer industry to take a nose dive. But it's been 7 years and my son is still bagging groceries? My 0ldest son gets computer job offers all the time and often out of the blue - I shouldn't compare - but I say this to prove there are jobs out there now. Anyway, if you might know anything, please leave me a comment or email me privately. Tks!