Just been diagnosed and struggling to tell people but exhausted with masking. Don’t know where to start

I agree with the above, don't rush to tell people.

It will take quite some time for you to mentally process your diagnosis yourself. You need time to understand how you have been masking and gradually try and put your real self forward.

Expect an emotional rollercoaster whilst you go through all of this. I think I am still on mine. The early emotions are wholly positive. Finally it all makes sense, you begin to understand past events and realise you weren't a failure. Then you might start to feel less positive and maybe even angry as you start to question why wasn't it picked up earlier, how differently things might have turned out if you'd known and had support.

The last thing you need while trying to process all this is additional pressure trying to figure out the response from other people. Inevitably they won't react as you expect them to, maybe not at all. You don't want to feel as if you're being observed, by other people looking for your autistic traits, at the same time as you're trying to bare yourself to the world without your mask. If anyone notices you seem different and asks why, that could be an opportunity to tell them. Otherwise take your time.

Its OK to not feel relief at first too - I found the process of the assessment and reading the report horrible and really upsetting. I already knew what it would say but having it all discussed and my worst failures written down was not a positive experience at all. I'm trying to decide if I should tell anyone at work - they will be good about it as its that kind of place but there is always a risk it may hold me back. Other than my husband I haven't told anyone in 3 months. 

Yes any emotions we experience are valid and everyone is different.

Trawling up past difficulties and trauma is horrible and upsetting. I think in my case the timing of the assessment process helped. It took around 6 months from the first of my assessments to receiving my diagnosis. By that stage I had already been through a lot of that upset and invested so much emotionally that I would have been devastated not to have received my diagnosis. The written report did not arrive until a few months after the diagnosis, so I did not have to try and process everything all at once.

Hopefully in time you may be able to reframe those 'failures' through an autistic lens and discover that they weren't failures at all. More likely they were the result of being in an autism unfriendly environment without the necessary social skills or support.

Yes any emotions we experience are valid and everyone is different.

Trawling up past difficulties and trauma is horrible and upsetting. I think in my case the timing of the assessment process helped. It took around 6 months from the first of my assessments to receiving my diagnosis. By that stage I had already been through a lot of that upset and invested so much emotionally that I would have been devastated not to have received my diagnosis. The written report did not arrive until a few months after the diagnosis, so I did not have to try and process everything all at once.

Hopefully in time you may be able to reframe those 'failures' through an autistic lens and discover that they weren't failures at all. More likely they were the result of being in an autism unfriendly environment without the necessary social skills or support.