Should I leave my wife for cheating on me, 4 times, and having another man's baby?

In November, my wife cheated on me with 4 different guys, and slept with each several times. She said that she was drunk at the time, every time. She never has really drank before, so the alcohol really hit her hard. Part of it was because she was underage, 20, and she needed these guys to buy her booze. I wouldn't. She don't drink anymore. Anyway, she got pregnant during this time, and last month had the baby. We were BOTH hoping it was mine. It wasn't. We had a DNA test done. Now, she wants me to raise the baby as my own. I forgave her for cheating on me, and I love "our" son, but, geez!! Am I doing the right thing by trying to let this all go, or am I an absolute FOOL, to say the least, for staying in this marriage? Before this all happened, I really thought I had the female of my dreams. Now it's such a mess of emotions for me, I just don't know. NO ONE else, (family, friends) knows that she cheated, let alone the baby ain't mine. Respectful answers ONLY! Thanks!!!!