It's been 4 years!!

Ok my oldest son's father, I cheated once and after I did the crime I got pregnant with our son on november 4 I told him I cheated and I was deeply sorry we found out I was preg October 28th I cheated on August 12th of 2011 I had my son june 6 2012 I told him I would get him a DNA test to prove that whole 9 months was his son! Well anyways he still hasn't let go and I don't understand the life of me why!!? He has a gf with another kid 4 months apart from mine my son is the oldest..if your wondering anyways I don't get it!?