Well, are you?  Do you even know what a Christian is?  Too many in the world. and even in Christ, do not know what a Christian is.  The world views almost all good people who believe in Jesus as Christians.   Many in the body of Christ view all members of the church as Christians regardless of how they are living their lives.  The truth is there is a difference between a child of God and a Christian, though we often carelessly use those terms synonymously.

It is true that every Christian is a child of God, but not every child of God is a Christian.  Let me explain.  A child of God is one who has been spiritually reborn.

John 3:3-5 (ESV)
³  Jesus answered him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.” ⁴  Nicodemus said to him, “How can a man be born when he is old? Can he enter a second time into his mother’s womb and be born?” ⁵  Jesus answered, “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. 

When a person is baptized into Christ, he immediately becomes a member of the spiritual family of God, that is, the church (Acts 2:47).   Once one becomes a child of God, he will be a child of God for the duration of his life regardless of how he lives.  He may lose his fellowship with God if he at some point stops walking in the light (1 John 1:7),  but he is still a child of God.

I have a son named Jordan.  Let us say that Jordan, who is a member of the Lord’s church, decided to leave Christ and live a sinful life.  I may discontinue to fellowship him by cutting off all association with him until he decides to repent and return to the Lord, but he never stops being my son.  Jordan will always be a child of mine no matter how he lives his life.  This is the way it is in Christ as well.  A child of God may be out of fellowship with God because of the way he is living, but he is still a child of God.

Now, what is a Christian?  Strictly speaking, a Christian is a child of God who is following after Christ.  A Christian is one who is imitating Christ to the best of his ability.  When a child of God stops striving to be like Christ, conforming to His image (Romans 8:29), he stops being a Christian.  Following Christ is what being a Christian is all about.

1 Corinthians 11:1 (ESV)
¹  Be imitators of me, as I am of Christ. 

Paul understood the importance of imitating Jesus.  He wanted brethren to follow his example in doing that very thing.  Are you imitating Christ?  You being a Christian depends, in part, on how you accurately answer that question.

While a child of God can be out of fellowship with God, there is no such thing as a Christian who is not in fellowship with God.  So, if there is sin in your life that is preventing you from enjoying the fellowship of God, that same sin is stopping you from being a Christian.  This does not mean that Christians are perfect.  We are, in fact, all sinners.

Romans 3:23 (ESV)
²³  For all have sinned and fall short of the glory of God,  

If we claim to be without sin, the only ones that we are fooling is ourselves.  John said, “If we say we have no sin, we deceive ourselves, and the truth is not in us” (1 John 1:8).  So, a claim to be a Christian is not a claim of perfection.

It must, however, be the determination of Christians to strive to live right.  Christians do not make a practice of sinning.

1 John 3:8 (ESV)
⁸  Whoever makes a practice of sinning is of the devil, for the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the works of the devil.

Christians would never try to undo what Jesus did on the cross.  Instead they live according to the high standard of the gospel of Christ.  That standard is Jesus Himself.  He is the goal at which Christians aim.  Paul is a good example of this:

Philippians 3:14 (ESV)
¹⁴  I press on toward the goal for the prize of the upward call of God in Christ Jesus.

The prize is heaven.  The goal, which we must reach in order to receive the prize, is living in the likeness of Christ.  He is the ultimate example genuine Christians determine to follow every day.

1 Peter 2:21 (ESV)
21  For to this you have been called, because Christ also suffered for you, leaving you an example, so that you might follow in his steps.

So, are you a Christian?  I’m not asking whether or not you are a member of the Lord’s church.  I’m asking if you are a person who has obeyed the gospel and is now imitating Jesus in your daily walk?  That is what being a Christian really is?