I was diagnosed as having ASD last year (mid 30s), although the consultant said I'm on the higher end of the spectrum because I appear able to hold down a job and don't have any major mental health issues.
I have strongly suspected for a number of years that I am autistic as many aspects of my childhood and adulthood fit the criteria. Like others, I pursued a formal diagnosis mostly for peace of mind.
Only my partner and maybe 2-3 other people know. I haven't told my employer as currently I don't have any major issues with the job. If that changes - like being asked to relocate to a noisy open plan office - then I will use my diagnosis to support my request for some sort of accommodation.
That was the other half of my motivation to get a formal diagnosis - in case I had difficulties or issues crop up in my job, then an actual diagnosis might help in getting employers to take my requests for help seriously.
I got the diagnosis through the NHS. I have always heard of how long some women have had to wait, but my timeline seemed relatively quick.
In October I visited my GP with a long letter explaining why I wanted a referral to a specialist and described what I felt was evidence of potential ASD. We had a chat and he said he would make the referral with my letter attached.
By November I had received an appointment letter saying I was to meet with a consultant in January.
I had my appointment in January plus a second one in March, and was given my diagnosis then.
There's zero support for adults who are diagnosed, but it's a relief to know exactly why I've been an outsider my whole life and why I have struggled so much with the sort of things other people appear to deal with easily. And my mental health has actually been very poor for most of my life. It's only been the last few years that I've slowly arrived at a more stable state since I accepted that I'm most likely autistic and started living my life around that fact.
I struggle with friendships and maintaining close relationships with people, but I've heard it can be easier with others who are also autistic. So I'm hoping I can meet more people like me and maybe find someone I enjoy interacting with. My partner says I write very long emails / messages which is probably what puts people off, and that makes me sad, but I'd like to think there's someone out there who would enjoy it like I do.
Oh, neither my ex-husband nor my current partner have ever met any of my colleagues and I hardly ever talk about my personal life at work. I do keep my different social circles very separate from one another and the few times there's been a tiny overlap (like two different people joining me for the same event or show), I've found it really stressful. 
I was also a bit weirded out when my partner said that I've never shown him where I work. He took me to his office once (I didn't want to go...), but I've never done the same. I don't see the point? Is this something people in relationships do? Neurotypicals are strange beings. 