You really fucked up. If you told her you're an asshole and don't deserve her. If she found out and you didn't tell her you likely wanted her to find out and you're still an asshole. Grovel, grovel, grovel and hope that she takes you back. If she doesn't, then learn from your mistake.

Dude, you were just lonely? What kind of BS is that?
Yeah sweetheart, can we just forget about it?...like, I was just lonely, sorry.

1. She won't forget. Are you kidding? All men, including myself, know WOMEN DO NOT FORGET.
2. Forgive? You better pray she forgives you.
Are you worth being forgiven? You slept with someone when you were "lonely"... and that only means you couldn't communicate your feelings. You writing this confession is evidence you probably do not know how to communicate your feelings.
3. 100% your fault and yours only.

Everyone deserves forgiveness. I hope she forgives you, only because she doesn't deserve all the hurt you've inflicted "because you were lonely."

that deserves to feel the full weight of your actions. I'm afraid I must tell you that it is this type of behaviour that can scar another for a very long time and cause a deep sense of mistrust in all others. Unfortunately this is how it is. She will never forget.

Tell her all of this, in person - not us.

Where do I start? "I know now that cheating on you was completely my fault." Umm, yeah, unless she held a gun to your head, you decided to cheat and you are responsible for your actions.

"I apologize for blaming you for my mistake" - how could it ever possibly be her fault that you cheated?

As for the "I was just lonely" statement, another poster has addressed that so I won't.

Buddy, you sound like a totally self-absorbed narcissist - and a guy who shouldn't be in a relationship because you are too self-focused to appreciate what you've done. To me, your words here sound shallow, like a little kid who got caught and is forced by Mom to apologize. It sounds insincere. (Actually, SO insincere that I'm wondering if this is a troll - and it probably is, looking at it again.)

Assuming it's not a troll - please do women a favour and avoid relationships - otherwise you're just gonna cause the women in your life a mittful of pain and they deserve better.

my former partner do that to me; I was 20 and I do not forget. I only trust a person once now. You are a P.O.S.

What a great apology, on an anonymous internet message board. You are a real winner. I think people ought to own the cheating. I cheated on my ex. She was a bitch and richly deserved it. She deserved the divorce too.