Hey there Hyper Boy
I agree, dont fret so much (easier said than done, i know).
If there is anyone you can talk to in person (maybe someone in your class?) im sure you'll find they will be thinking the exact same. You are not alone.I mean, the fact that you are on here (at 13 may i add) so worried, tells us all that you are definately going to do something great with your life.
How are you doing at school (you dont have to answer) its just, maybe there is a clue in there of why you are feeling so scared. Are your grades ok? What is it do you think is bringing about these feelings? Once you know (or think you know) then you can start trying directing your energy in to something more constructive. Have you thought about doing some kind of work experience for psycology, if its something you enjoy and want to do there can't be any harm in it.
Most importantly though, just be 13 and have fun with it. You have nothing to worry about