Wow. Pious much (him)? What kind of a person tells their GF that because of her he's lost all trust in humanity? Either he's a drama king or he is very, very mean. And if he had sex with the two women before you, did he get tested for STD's?
As long as he continues to see that T you will never be able to rebuilt trust since the T is who told him that you would never change.
Your last sentence was on the mark.