Like so many other writers, I'm doing NaNo this year. I started with a bang and wrote almost 5,000 words the first day and have been managing close to 2,000 words each day since. So I'm rocking in in that respect.
The problem is, I've written all this, and I feel like I still haven't reached the real start of the story. I've introduced all the key characters, I've introduced the world they exist in and I've set the key plot elements into play, but I still feel like the story hasn't really started yet and I'm not sure when it will.
It's only day four or five and it sounds like you're working at a feverish pace. It's NaNo. It doesn't matter what you write. The goal is to write. And you're doing that.
Sometimes it takes a little while to bed into your story, to find out who the characters really are, what their voices sound like. None of what you have already written will be wasted, even if you do end up cutting the first three or four chapters or dramatically shortening them later. That's what editing and revising is for.
So don't worry about it. They are not wasted words. They are your words and have helped you get to the place the story really starts, and having written them, you know your characters better, you know their unique voices, you know how they react to one another. Anything you write from here will be better informed because you wrote those words.
So keep going. You haven't failed at all. You've just done a little workshopping for yourself. I tend to do this too, with every novel I write. I get about 10K in, and realize I'm just starting the actual story. And that's even when I'm not writing at NaNo pace.
Be kind to yourself and just keep writing. The story you want to tell is there, and you'll get to it once your characters are ready for it.