Slippersmum I am so sorry you were forced to keep this secret.
I sincerely hope you will get some counselling to help you lay these feelings to rest. It is, as you know, no shame or guilt to be adopted, and I really hope you will fully embrace this whether you choose to tell people or not.
I am so sorry about your illness and hope you will get all the help with this. I know that I know nothing about the illness but having investigated various things in the past on the internet (unrelated, e.g. autism) that sometime the USA has much more information on medical factors and even though some things are handled differently their larger population size and shared language means there is just more 'stuff' on any topic out there! Sorry if that is all too obvious!
Anyway, back to adoption.....
Adoption UK might have some support for adults who were adopted
www.adoptionuk.org/
Your situation touched my heart and while Googling around I also found this....
www.pac-uk.org/our-service/adopted-adults/
You may be able to find a specialist counsellor...
www.pac-uk.org/our-service/adopted-adults/#spec
ans here is something called After Adoption.
www.afteradoption.org.uk/are-you-adopted-adult-or-birth-relative
It may be that most of this is about tracing birth relatives but some may be relevant.
I am not adopted but I am a mum to a child through adoption 9aged 4, a son) and birth child )aged 10, a daughter).
I had counselling for anxiety many years ago and found it very, very helpful and liberating.
Please do tell your friends now, if you wish to, but I really do suggest counselling first.
Your friends may or may not know how to handle the information and may not respond in the way you would like. Either by being too interested or not interested enough .... or perhaps even (I sincerely hope NOT!) resenting the fact you did not tell them sooner! They may also not understand why you chose to abide by your parents wishes and keep it secret or why you choose not to now!
Some of these responses might be totally inappropriate and unhelpful to you and so I think you need to build yourself up before telling people. You also have the illness and the impact of that to consider so please do get some help. I really hope everyone told would behave in the right right way for you.
I really hope whoever you tell feels honoured.
We have told our son it is his news to tell, but just warned him he cannot un-tell it. So at the moment (at 4) we have a mixture of friends who know (because they have known us all for ages) and newer friends who do not. Our son rarely talks about his birth family but we do encourage him to be open with us, if he wants to and we regularly see his foster family, who are very special to him.
Your message has helped me to see that it must be his choice, as he moved through life, (I know this of course but it reminds me JUST how important that is).
If he wishes to tell or not, and who and when. We will do all we can to help him and allow him to make the right choices for him at the right time.
I am so sorry your parents did not (for whatever reason) feel able to do this for you but I hope that whatever happy memories you have of your dad and memories and current time with your mum still mean a lot. My mum is 80 something and has dementia and my father died 10 years ago, so I know that elderly parents are quite hard, sometimes, to deal with anyway!
Bless you.