I don’t remember my teenage years

This is really weird and I’m just wondering if anyone has any ideas what it is. I have a good memory, can remember things from when I was 4-5. But.. from the ages 11-15 I literally don’t remember anything. I don’t know how many people I kissed, if I had sex, what teachers I had, who my friends were. I honestly just don’t remember. But I clearly remember after I was 15, I remember everything from there. So I’m really confused as to what is going on here. I’m only 20, how does someone forget 4 years of their life? No traumatic things happened to me