1 John 2.5 promises those who do what Christ tells them to will learn to love God more and more. That is the way to know whether or not you are a Christian.
Imagine taking a test where any answer given is deemed correct. We would not think much of the test nor of the subject. Every teacher expects their students to give them the same answer on their test if they wish to pass the test.
Every team expects all of the players to know the plays and perform them the same way if they are going to be successful. Every company expects their employees to know their procedures and perform them the same way so that everyone can more effectively work together.
God has given to us the Bible so that we can know the correct answers to the questions Who is God and what does He require of us.
While anyone can claim to be a Christian, and most people in America do, their understanding of God and what He requires from His people varies greatly. This variance leads to confusion among those who don’t understand God and are ignorant of what He requires.
God abhors chaos and confusion because He is Truth, Light and Holiness incarnate thus He reveals, He makes known and He transforms into perfection. A primary purpose of the Bible is to get everyone on the same page about the character, nature and will of God.
The reason Christianity looks so different among so called Christians in behavior is based entirely upon ignorance and rejection or acceptance and obedience to the clear teachings of the Bible.
We are free to decide what we will believe and what we will do but God has declared Himself the standard by which He will judge our thoughts and deeds on that day we each stand before Him and give account for the lives we lived on this earth.
He wants us to succeed at pleasing Him so has given us clear instruction to do that very thing; we just need to make seeking God through the Bible our first and greatest priority.