I committed a sin ages ago. Like several years ago. I don't commit this sin anymore. I'm 18 now. Once when my parents asked me if I committed this sin, I lied and said no. I didn't know lying was a sin at the time. All this happened before I became religious. When I became religious, I confessed this sin and the lying. Do I need to tell my parents the truth? It was something really embarrassing and I'm worried about the consequences if I told.

Go to confession and ask your confessor.

Exactly.