RSG, did you know OM was M? I don't remember that...
Anyway, that is not a R that is going to last, but knowing for sure may help you really drop the rope. im sure it was devastating to find out, it's ok to feel the sadness, but try not to let the anger take over, and DO NOT confront him, he is not worth your time, and you don't want to get yourself in trouble.
See a lawyer, find out your options, but don't file out of anger, you may need to to find out what is best for son, but if it doesn't matter, let the anger die down before making a decision.
M - 9 1/2 years 5/5/16 - Bomb drop - 3 week EA 10/31/16 - We sold house 01/10/18 - D Finalized