I'm 35 and was diagnosed just under a year ago. All my life I've had social problems, weird habits (flexing and un-flexing my fingers repeatedly, touching my nose a lot, making odd sounds kind of under my breath, etc.), flitted from one obsession to the next, became hyper-focused and fixated on an area of interest only to grow bored with it and wonder why it ever even was interesting. I accumulated vast amounts of information for no other reason than to *know*. (I read the dictionary from cover to cover. A few dictionaries, actually.)

The thing is, Asperger's had been described in the literature but didn't really exist as a diagnosis until I was in my late teens. I was never screened for it or tested for it; I was just labeled 'gifted' by the school administration and "that weird kid" by my peers. It was my giftedness that got me through my early adult years. people tend to overlook a few eccentricities when you're always the smartest person in the room. Still, I had trouble holding down jobs because of my inability to navigate (and complete distaste for) office politics. I have a job today because I own my own business... a handyman business because making things and fixing things are among my many obsessions. And it helps that I'm a perfectionist.

Seriously, 31 is not too old to be on the spectrum. It's not something you grow out of, but you can learn how to manage it and even put some of the positive aspects (intense focus, unique thinking, internal motivation, high fluid intelligence, being highly logical, etc.) to good use. I had talked to quite a few people, too, and finally got tested for ASD after ruling out, among other things, ADHD, depression, even psychopathy. The testing basically (for me) consisted of an interview with a psychiatrist specializing in spectrum disorder. There is a huge written test that many people take, and often interviews with family members or people who have known you since childhood are included, but in my case the doctor said (after about 20 minutes of talking to me) that those things would be unnecessary, that I was "definitely on the spectrum."

There's no medical test, and most doctors--and even psychiatrists who don't specialize in spectrum testing--don't know what to look for. As far as fixing it goes... no, there's no pill or direct treatment (though you can treat the often co-morbid things like anxiety, hyperactivity, and depression). But many of us on the spectrum lead full and vibrant lives once we learn some coping skills and embrace who we are.

There's a test on PsychCentral you can take that may help you decide if you should get tested or not.
Autism / Asperger's Quiz