Questioning Christianity

I have been a Christian for 20 years and have begun to question my faith. This is causing me a to lose my mind. Listen, can anyone convince me that Christianity is the right track to follow. I know this is a Christian sub, so it's going to be bias, but i need an argument with fact and logic. I need a convincing argument, please and not just bible verses, I actually need something substantive.

One thing that does not sit right with me is the fact non-Christians are said to go to hell no matter the good deeds they do, due to the fact that they did not accept the religion or were not born into the religion. It doesn't sit right with me at all. And Christians who commit genocide, murder, and other bad deeds can be in heaven because they accepted Jesus before death.

I need a convincing argument about the religion, validity of the bible, and thousands of different denominations. Also why is slavery in the Bible?