Being a Christian man doesn't make you, me, or anyone else a sinless man. There has only been one sinless man to walk this earth and He died for our sins that we may have everlasting life.
Satan will use every trick in the book to get you to turn away from God. I believe temptation is probably the number one tool in his arsenal.
Read or reread the book of James. It really is a guide on how we should live our lives. It helps me.
Ask God to help you overcome this and and He will.