steal watever you have thats his, sell watever you have of his that you dont want, sell his house and keep the money, tell all of his friends he has become homosexual, complement the wife on her pregnancy (when shes not pregnant), change your name, and move to italy or france or somewhere with cute guys so you can get over your exhusband :) hope i helped!
It is called bigamy, when someone marries again, without getting a divorce. Hire yourself an attorney, take everything you can and get yourself a divorce. If you really want revenge, have him arrested and brought up on charges. It is against the law, what he has done.
Unless you are trying to get marriage counseling...your decision but wouldn't do it myself.
You need to go get an attorney and stop taking anymore advice from anyone else. Let your attorney inform you and guide you. The longer you wait the more mistakes you make...like sleeping with your husband even one time since you discovered his dirty secret. In many states, marital infidelity is considered forgiven if you resume sex relations with the guilty party. In this example you would lose the legal advantage for infidelity. Now since polygamy is illegal he will face criminal charges if you chose to expose it. My advice is to can him as this is unforgettable not to mention totally disrespectful of your legal marriage here in the states.