Please tell me I'm not alone...

Now that we're actually TTC#2, I'm terrified. I feel like I'm ruining my son's life. Ruining our perfect, simple, family of three. I know it's dramatic but I'm so emotional about it. It's like I know I want to have another baby, and I know I want our son to have a sibling, but I don't think I'll ever truly be ready for the change. And it makes me feel awful, like there's something wrong with me. I'm only 27, and this will most likely be our last baby.