My wife cheated on me!!! so depressed!! aghh?

im usually on here to help students with their history questions but i can't help but ask for help in this matter. i'm so depressed and i don't know what to do. we've been married for nine years and i'm very faithful and loyal and have been to her since the day we met. we have a five months old son together as well. yesterday she told me she is unsure if i'm the father. what the f*** am i suppose to do? please help anyone. she's been cheating since the day we married and i can't handle this! i'm on the verge of cracking this computer. i dont want to leave for god sake i love this woman.