PLEASE 🥺 I did a terrible thing when I was 13 (a year ago).

Every month since I did that, it has been so hard. I lost friends and I can't talk to people properly anymore. I cry every day, feeling like I have no future left. Whenever a good thought or a dream comes to my mind, that bad memory pops up and ruins everything. If anyone finds out, it's over for me, and I am so scared that I might end up going to prison. What should I do?