How I found out my pregent wife was seeing another man

Whenever I see news of people cheating on their partners on social media, I always show my wife and we will laugh over it. In my mind, I always say that my wife will never cheat on me, that's why don't bother monitoring her or check her WhåtsAppp conversations with people or who she is chatting with even though she always check mine. I never knew she was sleeeping with a man until the day I checked her chat and found out the man she was sleeping with i trailed them to the h0tel they normal meet when she says she is going for shopping. The worst is that my wife is pregnant and she's sleeeping with another man!. I am totally Sh0cked and confused on what to do. I don't know if I am the one responsible for the child she is carrying. Please what should I do. Should I forgive her or send her packing....