Writing a story on the experiences of my life, and didn't even realize it?

I was just wondering if you've ever gone off writing and then discovered you were writing about yourself or an experience someone you know has had and didn't even know it?

You can read under this if you want to.

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It's about a young boy who was bullied by this one boy all throughout grammar and middle school. He'd often be taunted, given nasty gestures, and even beaten badly. He also had a bad home experience. He was a total recluse and found joy in only music. Before he could graduate high school he dropped out and became a helpless drug addict. One day, on the streets, he met a familiar face who ended up having to take him to the hospital after getting stabbed. After a long while the guy realizes the man who he became friends with (the one who took him to the hospital) was the boy who bullied him. He finds that the boy who bullied him only bullied him because he didn't know how to show that he wanted friendship. He, too, had a bad experience with family, and didn't exactly know how to show his feelings. Of course, there are quite a few more events but I wanted to make it as short as possible.

I went almost three days with non-stop writing of this and JUST found out I was basically writing my entire life story. Even the charters are almost just who they are in real life. The place where it's set (Seattle) is even exactly the same. I didn't even realize I wrote my life story up to this point until just a few minutes ago.