This question can be hard or easy for people. For me I believe everyone is a Christian to start off with as I believe God created the earth and us. However you are called a non-believer or Athiest if you don't . Some don't believe at first then they do later in life and some start believing and then circumstances make them stop believing. Being a Christian is very confusing when everyone has a different opinion about it and only yourself know how you feel. Do you believe in the 10 commandments? If you relate that to real life they are sins .But if you believe that God and Jesus will help save you and you ask them for guidance , you are already a believer , because non-believers generally don't think about prayers . Hope this helps and this is based on my personal thoughts. God Bless.