find a lawyer or legal aid
As far as I know (I am not a lawyer).
There is NO 自动离婚, ever. It does not matter if you two have been separated for 50 years. Marriage is a legal contract, and MUST be terminated by a court order, YOU MUST GO TO COURT.
You CANNOT 单方面离婚. All divorce must go through court and your spouse will be given opportunity to respond to your claim.
It appears that you have made a mistake. The right course of action is to CORRECT your mistakes, NOT trying to cover up your mistakes, because they will NEVER go away.
You may be punished for your mistakes, but I am sure that the government will treat you more fairly than 跟你假结婚的人. Even if the result is "取消我的身份,还赶我回去中国" (I doubt it), at least you will be FREE. Otherwise you will be a slave for the rest of your life.
In any case, FIND A GOOD LAWYER, and good luck to you.
For all others who are considering 假结婚. Let this be a lesson that 假结婚 is not easy money. When people say you are signing your LIFE away when you get married, they are not kidding.