All I can say is I've been there, and I know how you feel. I was pretty taken by surprise and I felt just as devastated at first, and it was a difficult road but I learned to quell my fears and try to trust my wife when she said she still loved me and didn't want to leave me. The jealousy took longer, and it's still not perfect. I don't really get sick anymore when she wants to see another man, but sometimes I get mad about it, especially when she doesn't communicate with me when she planning on meeting a man.
You're entitled to your feelings, and they're valid, but trust, communication, and time will sort them out one way or the other.