What is the purpose of religion?

Religion has absolutely been puzzling me lately.

First of all, there are so many different religions- and with it accompanies a whole history of vast populations of people believing so strongly in their religion- that they are willing to lay down their lives (in whatever way) for it.

Problem number one: they can't all be right- which means that either everyone is wrong, or a very few people are right and the rest of the world's population is wrong.

Problem number two: how can we know for sure which one is right?

I was raised Catholic (so i have fundamentally Christian beliefs inbuilt- however i don't think that stops me from being objective about the religion. I am a pretty openminded person afterall.) Then my secondary school years were primarily occupied by strong minded Atheists and Christians debating the debacle that is "Does God really exist?". Currently i attend a university that is dominated by students of the Islamic faith. Perhaps the influence by opinionated people of different belief systems has caused me to doubt myself.

Now i sit here, 19 years old, realising that i don't know a whole lot about my supposed religion.

I can see how religion can influence the course of your life- so i think it is imperative that i find out exactly what i believe.

Originally i thought if i was determined enough i would find out which religion was true. But the more i've looked into it, i see that evidence for or against each religion consists primarily of people's views. Nothing more concrete than a person's opinion (in addition to some historical figures, events and artifacts to back this up). Can i really put my whole belief of what i perceive to be the truth of the universe on the words of what another person has said? How am i to choose which person to believe?

I have no idea. I shall update you all when i figure it out, if i ever do.