Heartbreaker

This is my story i am in a relationship in the beginning there would of been nothing i wouldnt do for her .over time we had some problems .then we moved south and i still had resentment about the thing in our past .we had a falling out and i had no place to go i was very mad then went to prison for 16 months and she stood by me the whole way. She didnt even date when i got out we had a long distance relationship needless to say i strayed and gave my self to someone else . this boke her heart when she was told about it of course i denied it and thought i could lie my way out but after seeing how i broke her i told her now i am so ashamed of my action i want to make thing right but im confused about everything and dont know where to start i cant stop thinking of my own self pitty how can I help comfort her i dont know where to start