It is difficult to provide a firm answer without knowing more of the facts. The good news is that the legal validity of any purported transfer of your 50 percent interest will be scrutinized by the court as part of the divorce process, and can likely be “un-done” if necessary, once fraud has been established.
The court will review the pages you signed, and the contents of the attachments which apparently transfer the shares. The court will also look at the overall circumstances at the time, including the reasons you were asked to sign the documents, any agreement you may have had together, whether you had independent legal advice, and whether you were under any pressure or duress. This last aspect can also consider the nature of your relationship with your husband, including any past pressure or coercion, and whether there was an unequal power balance, particularly in connection with financial matters.
With all that said, if you think that you have been the victim of fraud at the hands of your husband, you should see a lawyer immediately to get fact-specific advice.