relinquish of parental rights

My sons father and I had a very rocky start when our son was born.  I honestly had made a very life altering decision to let his biological father have sole custody of our son.  He has since married and has also passed away.  I feel as though I was pressured into sighning off my parental rights to his widowed wife.  Her actions from his death until present have become horrifically spiteful and she has now completly abandoned our Nikos and mjyself Bobbi Jo) son, to move to another state without him.  I was under misguided council professional advise on the legal right actions to address for his return to myself (his biological mother).  There is no indication of my sons where abouts and I am beyond greatly concerned about his care, safety and health (