Ready to publish, but self-doubt is crippling me

I've written a sci-fi book that I have formatted for ebook and paperback, but I can't seem to make myself hit the publish button. Dozens of people have read it and they all enjoyed it, so I am not sure why I'm having so much trouble. Is it like this for everyone with their first book?

Any advice would be appreciated. Thank you!

Edit: Thank you, everyone, for the wonderful advice. My book is now up for preorder. I feel a lot less nervous about it now, oddly enough. I'm glad I went ahead and did instead of stressing about it longer! Now to market it :)