My advice is to accept and respect you needing extra time or effort to process what you think and want and how to relate it to what you think other people want.

When you feel the need to respond immediately to all demands, the "safe" option will always be to do what others want.

Find some phrases that work for you if you need to respond to something before you are ready. Something as blunt as "Sorry, I think slow. Give me an hour" might even work. Almost always, people wanting something from you are very patient if they feel that you have understood them.

If people can't give you that patience, that's a bag of red flags. They are consciously or unconsciously trying to exploit your good nature and are not to be respected.

Hi there! I can relate. Have been in a similar situation and am actively working on getting better. I don’t have a book for you, sorry. I‘d be interested as well. But I can rell you what I do to alleviate this problem:

Working with a therapist to talk about situations where others walk over me or confront me and actively work on strategies of defiance, reflection, discouraging such behavior and so on.

My wife also has the express task to listen and intervene if I‘m reporting being exploited. That is, her telling me to do something, not her intervening on my behalf.

It does help but a good book would interest me as well. Good luck with your journey.

How to Lose Friends and Infuriate People by Jonar C Nader

It’s sold as a business management book, but has some great tips on communicating with idiot normies.