It doesn’t “sound dumb” to me at all. You suffered a major loss when you were 10. You say that you used unhealthy ways (like cutting) to cope with your feelings of grief and confusion. Although it was an unhealthy way to cope, it did work for you. Unhealthy coping distracted you from feelings you were unprepared for and that were too big for you to deal with.
Now that you’ve stopped cutting, I think psychologically you are going back to the time of your loss to try to cope in a better way. But, it’s as if the only coping skills you know you can count on are the skills you used at age 10 — playing games and reading.
Your challenge now is to make up for lost time. You didn’t spend the last 4 years developing age appropriate coping skills. To get on with your life, you do need to do that.
I think seeing a therapist is a good idea. A therapist can give you some coaching and support while you catch up and learn the skills you need to go forward. She can also help you use those new skills to deal with the feelings and changes that happen at adolescence.
I’m very glad you wrote. Your letter indicates insight and intelligence. I think you will make good use of therapy.
I wish you well.