He's not going to change and if you were to marry him, he will have affairs on you left right and centre. He did NOT learn a lesson or feel remorse the first time he cheated on you and went on to do exactly the same thing again, Block and delete his bullshit and start the rehab process of cleansing yourself from the habit of having him in your life.
(although you don't state that he was sexting but simply "texting" so I'm not sure where he actually did anything wrong. What were the nature of the texts?)
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion