Like Libz said, you're not stupid at all. Revision sucks, but you've got two whole days at the weekend to cover the topics and do some practise questions. But don't stress, and take lots of breaks :)
You're not weak, and I hope that going to uni helps you to see yourself a little differently, and that you learn to believe that you are a good person. You're very significant to many people, and hopefully you will be able to see that soon :)
Also, FREAKING EXCITED FOR GETTING TO MEET YOU FINALLY!
ahem, *turns off caps lock* :p