He cheated with me.

To make a long story short, I got in a secret relationship with my best guy friend who was already in a serious relationship. This lasted 7 months, I broke it off 2 weeks ago because I honestly couldn't handle the guilt anymore. I feel so shitty. His girlfriend is so sweet and doesn't deserve this. No one deserves to be in a situation like this honestly. I blocked him on all socials even though we were close friends before this all went down; I literally just couldn't handle feeling like that anymore. I'm not trying to make myself out to be the victim because obviously I'm the crappy person in this situation but what do I do? Is there anything I can do to make up for my mistake? I literally never want to be in a situation like that ever again.