Not legally divorced, expecting a child not of legal husbands. Does child receive legal husbands name if paternity is not being questioned?

The simple answer to your question is YES.  The law in Illinois presumes the child born during the marriage is of the marriage.  You are, however, asked as part of any divorce prove-up about any pregnancy and whether the child is of the marriage.  From your statement, the answer, should that question be asked, is no.  Since the Court's do not want to leave a child without a father, the next question would be "who is the father?"  At this time, there may be an inquiry into your living arrangement, child support, and the like.  Properly done and under the rights facts, the divorce can go through with a finding the unborn child is not of the marriage. So: Option A is to commit purgery by saying you are not pregnant, which is not really an option.  This is a felony and no lawyer can subborn purgery.  Option B was stated above.  The recommendation is for Option C. Option C involves securing a family law attorney and being pro-active.  Working out all matters with your Husband, including the non-pregnancy (as, among other issues, he would not want to pay support for the unborn child).  File an action in paternity against the true father.  He should admit the child is his; and the naming can be part of this action.  This may be more expensive, but it gets you legally divorced, obtains the father's name for the child, and demonstrates whether the 3rd person is committed to being a father. Child support would be ordered as well.  At the very least, there can be an Affidavt or Admission of Paternity filed in the divorce case.  The result would be similiar, if allowed in your County.  This may all be done without an attorney, but we recommend that you first consult with an experienced family attorney, who should be able to be referred to you by your County Bar Association.  In that way, you can determine the best way to proceed in your County.