Heartbroken and spiteful..what to do next?

well I crossed the line that you never cross. my best male friend became my secret lover became my son's father in a matter of 5 years we have had a secret affair that became not so secret. now suddenly he has abandoned me. and our son. our baby is now 3 years old and after years of fighting to have a life with us do to and on again off again relationship with another child's father and I finally gave in than suddenly there's no contact. he just forgot about us. the stories I hear jus have me ready to do the foulest of deeds to make myself not hurt so bad. any advice.. how do you heal a spiteful broken heart