Don't worry because I feel the same way you do. I had a great idea for a website and started making the concepts. While in the process of making a website I feel doubts because it is an entirely new concept that may not work. But in the end I still continue making it and asking everyone's opinion and from there I got the impression that I'm on the right path. My advice to you is you ask for the opinion of others and you will have a great result.