Maya — As Susanne said, you don't have to make any big decisions today...but you should start building your support network. Many here have felt tremendous relief just talking to someone they trust. Someone else suggested journaling, which I think is a great idea.
Divorce is painful...but I am quite certain it pales in comparison to the pain of being cheated on and having your physical/mental health compromised by someone you love. Kids are tremendously resilient...I know I wouldn't want my own mother (or my daughter) to suffer through this kind of pain. Your happiness is important, too (for you & your children).