Eva, I spent the night before doing exactly what you did, trying to talk myself out of going. Once you have been, you will wonder what you ever worried about. There really IS nothing to be scared of. Everyone is there for exactly the same reason you are. There will be people bigger than you, and smaller than you, but they all have exactly the same goals as you. They want to be able to lose weight and still be able to eat all the foods they enjoy while doing so.
This is the first step on your journey, and it might feel like the biggest one of all right now, but soon, it will be a step that is behind you, and you will be well equipped for the rest of your journey.