I think most of us have done things when we were younger that we would never do as the people we are now. I know I have- I have plenty of cringe-worthy moments from my youth. This sounds like it is bothering you so badly though that it does sound like something you need to talk to someone about. You already said it isn't something you would ever do now so maybe having someone you really trust tell you that you deserve to forgive yourself would help. Hugs!
__________________
"If you have men who will exclude any of God’s creatures from the shelter of compassion and pity, you will have men who will deal likewise with their fellow men." — St. Francis of Assisi, 1181-1226