I would keep my damn mouth shut. If you tell her you cheated, you're out of there. If not forever, then for a long, long time. Every single bridge you two built will be burned. It doesn't matter if you tell her now or she finds out a year later. You're going to get dropped. It's the same result either way.

All you guys saying to come clean, I don't know what you're thinking. If this girl has a shred of self-esteem, she'll kick him out in a heartbeat. "Oh but maybe if you're honest and she forgives you your relationship will come out stronger." BULLSHIT. Only needy and clingy girls would stick with a guy who cheated. And those kinds of girls aren't worth dating.

OP, keep your mouth shut and pray. You fucking PRAY.