Hello fellow Belfastern! Good luck with the GCSEs for next year. No need to be nervous, just keep up with revision (I should know - I've left it to the last minute and crammed on more than one occasion and never came out with as good a result as actually taking the time to sit down and learn gradually!) and it'll all fall into place when you take the test.
Do you mind if I ask you which school you're at? I don't know of many of them, I just know them by colour of uniform!