What's our purpose of life?

I'm pretty sure almost everyone know the movie 'constantine'? well, I watch it on TV just hours ago. Think this is my 3rd time watching it. It's a really good movie. This movie makes me think of our purpose of life.

I often ask myself..What is my purpose of life? Is it really true that there's heaven and hell? Is there a god watching over us? Is the whole meaning of this world created by god just to fight over souls with the devil? I do believe in god because that's how i was brought up but deep down i always have doubts.. questions...

Everyone have their own believes but who is there to tell us whose believe is right and whose is wrong. My mother always tell me that we should spread the words of gospel. We should believe so that when we die we will go to heaven and not suffer in hell but who is there to tell us for sure that there is heaven and hell? So does that means our purpose of life is to live our life happily, believing and preaching the gospel so that when we die we can go to heaven? So wouldnt it be better if i die when im a baby. cause then i'll go straight to heaven and save all the trying to get there. Since i dint die as a baby, can i live life just sleeping, eating and believing cause for me the things i enjoy most in life would probably be sleeping and i'll have to eat to continue living. If god sent us down to suffer for all the sins then would our purpose in life being in this world is to suffer? But then why do some people have a better life than others? Some people who are born in a privileged environment live their life not having to suffer at all. Why? Are they less sinful than others?

Someone once told me that it is better to live your life believing than not believing because there's nothing to lose if you just believe. There isn't a price to pay so you'll either win or not win but not lose. Therefore, I choose to believe. I dont have a choice of not having to live my life. I cant kill myself cause that will be painful and I'll go to hell if there's one. So, what's my purpose of life? I'm still figuring it out...

Anyone out there that knows and is sure of their purpose of life, please... tell me... So that i'll know how to find mine.