NO. If you log into the NBME licensing services website and pull up the extension form as a PDF, it clearly states: "you may only request one extension per registration."
No, forget about the cold feet just take the exam! {only thing I can think of is if you can prove Death of the closest relative in your family or a morbid accident and even that is very shaky..} {if that was allowed it would become a futile cycle} get out there and fight, honor your screenname!! Geez, it aint no joke!