I have a BA in Psychology, and because of that I could call myself a Psychologist. However, that doesn't make one. Maybe it's the first step, but that's about it. lol Further, it would do me no good to become offended if someone told me that I wasn't one. I don't understand why people get "hurt feelings" over someone telling them they are or are not something. If you meet the criteria for the title of something, then who cares what someone thinks. If you haven't then meet it, and move on.
Merely because someone calls themselves a Christian does not make them one. Meet the criteria God sets for being a "believer," and you can have confidence that you are one. "I (Jesus) am the Way, the Truth, and the Life; no man comes to the Father except by Me." John 14:6; Salvation is found in no one else, for there is no other name under heaven given to mankind by which we must be saved." Acts 4:12; And everyone who calls on the name of the Lord will be saved. Acts 2:21. There are countless others, of course....that mention the need for repentance (if you confess your sin He is faithful and just to forgive you of your sin and to cleanse you from all unrighteousness), the need for works (faith without works is dead), etc. However, Jesus is the only mediator between God and man. He is the only reason that the spiritual separation between a Holy God and sinful man is now closed, and we are in right standing with God.
Of course, "believing" that Jesus exists is not what the Scripture means. Believing means to trust and rely on. It means to make Him Lord of your life.…I John 5:3 By this we know that we love the children of God, when we love God and observe His commandments. For this is the love of God, that we keep His commandments; and His commandments are not burdensome.
4For whatever is born of God overcomes the world; and this is the victory that has overcome the world-- our faith.…" Of course, not the Mosaic Law, but to love God and love His creation. When one is doing that, then everything else will fall into place. If you love someone, you won't steal, lie, cheat, etc., them. If you love God with all your heart, soul, and mind you will be obedient to that which He asks of you.
1. Acknowledge that you are a "sinner," born with a fallen nature, which spiritually separates you from God.
2. Repent of living a life according to your own ways and not God's ~ the God of the Bible.
3. Recognize that there is nothing you can do to 'save' yourself, and that only by a one time offering of Jesus upon the cross (without the shedding of blood there is not remission for sin), we can stand righteous before God because the judgment that was upon us has been paid in full.
4. Make Jesus the Lord of your life.
Then, you can call yourself a Christian...