how can i ever forgive myself

nearly 6 months late, after so many lies, i finally told him i cheated. I was with friends, got drunk, and made out with another guy. Ive felt so bad about it. For months i couldn’t sleep. we broke up months ago but i he had suspicions because of all the rumuors and i think he needed closure. So I told him. I’ve apologized profusely. And looking back i was way too immature to be in a serious relationship. Im 15 btw. But i feel like i will never forgive myself. ever. it’s been forever and i still feel so bad. i was thinking I could maybe go to confession (i’m catholic) to get some closure. I just feel the worst person on the earth

edit: these are all really good advice i appreciate it thanks