Welcome to this place. I'm sorry for what you have gone through and I know a lot of underdiagnoses happened and happening, including me never a cheerful bubbly one since I was a kid. We have our own bumpy roads to travel on... I agree with Geoff that having a diagnosis can be a great relief...
I'm glad that you hold hope for your future. I'm learning to notice and enjoy small cheerful things which indicate a sense of hope which did help me a lot, I wonder if you feel the same.
hope you enjoy being here and all these friendly talks!