So me and my fiancé have been together for 2 years. We have a pretty good relationship but a month ago I found him cheating on me with his ex. He does have a child with her but, she never lets him see his child because she's that type of mother. My fiancé does everything for his kid from buying clothes, food, etc..  He sent kissy faces telling her he Loved her and loved his son. He told her that he wanted his family back and so on and so on. When I confronted him he said the reason he did everything was because he wanted to see his child and the only was to see his child was to sweet talk her and make her believe him when he was lying. I don't know what to do. He basically cheated on me but told me he did it for his son. I need advise. ASAP ):