J.R.
You can try doing an online search for the mother in the online white pages, or if you know what state she lives in, call 411 information direct. You can also check Facebook. A similar thing happened to me when I was had my daughter and found out that "daddy" had a fiance, who had a child 9 months after my daughter was born. I found out her name when I received an insurance card through the mail from child support services. I called 411, got her phone # and called her. She was just as interested to find out about me as I was to find out about her. You didn't go into detail regarding your situation, but it sounds like your husband is being pretty sneaky. You have a right to know about any other children he may have, just like your child has a right to know about any siblings. If you are able to make contact with this woman, she may become someone who can help share information with you in the future in regard to locating dad for child support. I hope it doesn't come to that for you, but doesn't hurt to be prepared. I wish you the best.