I need help..

I have legitimate questions about Christianity and Bible stories, but when I tried to ask my youth pastor she got mad. here's my main question, maybe someone can answer it for me. what happened to people before the concept of Christianity existed? the concept of god and Jesus wasn't around, so they had no way of believing in it. did they all go to hell? that seems very unlikely, but according to the church those who don't believe in God go to hell. for hundreds of years Christianity didn't exist. what happened to those people?