Take a DEEP breath and take it from those who have been where you are now...
The important thing right now is not making stupid mistakes. In other words, stay clear of drugs, use alcahol in moderation if you must, be good to people and work hard. The rest will come. Do NOT go off and do dumb stuff and try all the previous 'forbidden' things...sometimes things are forbidden with good reason!
As for the whole belief thing, you will be adjusting that for the rest of your life so dont rush to figure it out, it doesn't really matter that much.
Life is not about what you believe in your head but about what you DO.
Too much emphasis is placed on 'the meaning of life'. There is no devine meaning. We are here, we breed. Our job is to make our life good for ourselves, those we love and those we choose to help. It is not a dress rehersal for the so called next life, so make it a good one.
Oz