Feeling hopeless after diagnosis

I posted a few months ago after being refused a diagnostic assessment on the NHS. Although my GP and an NHS psychologist were keen for me to be re-referred with more information (because the referral was refused in part due to my GP's mistakes) I had lost faith in the local assessment service and opted for a private assessment.

The assessment service I used was great, the people were lovely and I got my diagnosis on the same day as the assessment. And for about 10 days after the assessment I felt much better - no longer in limbo, waiting to know, therapy plans could now be put in place in the NHS (I have an appointment in about two weeks) and people were happy for me that I'd finally got an answer in the form of my diagnosis. I felt like I could finally start to make some changes to the way I manage my mental health to try to cope better with my anxiety (I was doing things that were really unhelpful for anxiety triggered by sensory sensitivities) and depression.

The assessment service sent a draft of the diagnostic report for me to read through and I found it really hard to read the descriptions of the social and communication mistakes that I make and of the difficulties I've had through my life as a result of my undiagnosed autism. It actually said plenty of positive things too and stressed the neurodiversity model, which I do believe in. However, since reading the report I've been struggling with feeling very depressed and hopeless, with lots of thoughts about being a horrible, anti-social awful person (which I know aren't actually true, but I seem to be unable to stop feeling that way about myself).

I don't know if it's a result of reading the report, or something else. Maybe because the effects of having a lifelong diagnosis are starting to sink in, and feeling the grief and loss associated with the effects of undiagnosed autism? It could also be triggered by going away this weekend for a week, even though I feel that it is manageable, or a subsequent visit from my parents (not an easy relationship, though they do care - they just can't seem to get it right), or the fact that all the people I would call on for emotional support are away on holiday and not accessible for help.

Did anyone else go through these feelings after diagnosis? Did you find anything helped? I can see that there will be positive things to come but I can't seem to translate that into feeling better.