Honestly, there's not much benefit to seeking an actual diagnosis and I don't know that I'd recommend it. My experience was pretty invalidating all in all; most psychologists, if they recognize autism, only do so in extreme cases or in children. I was in therapy for PTSD after my roommate committed suicide, and when I mentioned that an aspie friend thought I was on the spectrum, the first person I was meeting with said that didn't fit because I "seemed to care about people." Huge misconception about ASD, but even psychologists believe it. Then I was seeing a different psychologist and I was lucky in that she had worked extensively with young adults on the spectrum, including females (it presents differently in girls than in boys); she worked with me all summer on the trauma, and we went through the DSM criteria for Aspergers (this was before the DSM-5), and she basically said that yes I have it, but she knew it was changing in the DSM-5 and didn't know yet what it would be. She also said that throughout the summer I'd learned so many coping mechanisms that the symptoms that were present might not be easy enough to detect for a diagnosis, and that she didn't recommend an official diagnosis for me because I wanted to go into medical school and it might affect my ability to get licensed.
I'm a very mild case, but I'm also more and more confident it fits as time passes and I learn more coping mechanisms and learn more about the disorder. Later psychologists (I've seen several because of location changes) have said it was possible I was on the spectrum but that I'm so high functioning they wouldn't have picked up on it, or that it only shows in certain contexts. Honestly though, in social settings it DOES get noticed - friends on the spectrum have asked if I was because of behaviors that stood out, friends who knew me when I was informally diagnosed said they'd wondered why I hadn't been evaluated years prior, and I've learned to recognize things where ASD makes so much more sense.
My point is, if you've made it to adulthood without diagnosis, it would probably take a special psychologist to recognize it in you. Some will think that caring about other people, or doing well in school, or being able to maintain a job, or having had relationships, means it doesn't fit you - when what they should be looking at is HOW you go about all those things. When I figured out I was on the spectrum, a LOT changed; I understood why things were happening, and was able to change them. Understanding my challenges has helped me to use them to my advantage. That, and the fact that the woman who was confident had I was on the spectrum was the only psychologist I'd worked with who had experience with young adult females with ASD, makes me pretty sure of my diagnosis. But it's informal, so that if I ever seek a security clearance or medical licensing etc I won't face the stereotypes that are so common.
If you would be okay if someone told you that the fact that you were able to call and make an appointment with them means you're too socially capable to have ASD, or that you're too capable of conversation (even though therapy doesn't require timing or interaction, just monologue) etc then you can try. They may give you some clinical tests (you can find the Autism Quotient online, that's a common screening), will probably take many sessions to get to know you enough to feel they can evaluate, may want to talk to a parent about early childhood. But if you can trust your own judgment and don't need the formal diagnosis, then I recommend reading up on it instead. See what fits you, what techniques worked for other people, how you can better understand yourself. For me, everyone who discarded the idea because of stereotypes that aren't necessarily true was very invalidating and very hard to hear. I could have handled much more easily someone saying they didn't feel it fit me for other reasons, but misconceptions that I knew from my research were misinformed really bothered me. It's hard to trust someone to help you if they don't seem to know what they're talking about.
Good luck!
