From what the questioner has shared, there are a few points that I'm not quite sure I understand, and it seems like there might be a bit of a contradiction. I would love to ask the questioner for some advice.
The questioner says that he is "cowardly and timid," but also "not self-deprecating" and "has friends." It's so interesting to me that he judges himself as "cowardly and timid" when he has friends and isn't self-deprecating. Have other people around him (family members, friends, classmates) made similar comments about the questioner being "cowardly and timid"?
The questioner said that after the age of ten, they began to experience "language expression difficulties," but "personal abilities such as storytelling...are good." So, in what situations and when communicating with whom does the language expression difficulty occur? Is it that they cannot communicate normally, or is it that what they express is not what they really want and goes against their inner thoughts?
The questioner is really struggling with why his personality has changed so much. He's not worried about the current "weak" personality causing trouble in life and work. He's just looking for answers. So, it's really important to him to understand why this happened.
The questioner said that nothing major happened when he was nine years old that was so serious that it suddenly changed him. In the book What Have You Been Through? Conversations on Trauma, Healing, and Resilience, the author suggests that it's so important for younger people to rely on their caregivers—parents or other adults—to help them understand the world.
He may not understand a specific word, but he can feel the non-verbal part of communication, such as tone of voice. He can feel the tension and hostility in angry words and the exhaustion and despair in negative words. We may not remember specific events or people, but the feeling of being hurt is deeply imprinted in the brain and is associated with specific scenes, character images, speech tones, etc. These early experiences have a significant impact on people, and once they encounter that specific scene, they will trigger feelings of being hurt.
I really think that if we have to find out what made the questioner change so much at nine, this could be a good place to start.


Comments
I can relate to feeling like you changed overnight. It's strange how sometimes we just wake up and everything feels different, especially at that age. The shift from being confident to timid really took me by surprise too.
It sounds like despite the change, you managed to hold onto your selfworth through your academic performance and personal talents. That's really commendable. Sometimes it's those hidden strengths that keep us grounded when everything else feels shaky.
Transferring schools is tough, especially if you feel out of sync with everyone else. But it's amazing how you kept your circle of friends even while dealing with such a challenging transition. It shows there's a lot more to you than just what you're going through.
Feeling like you've suddenly become someone else can be disorienting. There doesn't always have to be a clear reason for these changes. What matters is how you move forward, and it seems you found ways to cope and stay connected with others despite the odds.