OP, I totally feel you. I'm right there with you. I'm not like, a creative genius who oozes paintings and sculptures and fashion design and amazing character design talents out of every pore constantly.
I am quite creative, but also analytical, a perfectionist, an outside-the-box-thinker, great with line/shape/color/type, and an avid appreciator and critic of media, fashion, film, art, music, etc.
But there are always people who will seem "more creative" than you, but you know what? They are differently creative. They probably have different strengths than you, and I guarantee that they have different experiences. Maybe they're older than you. Maybe they have focused their entire life on art, whereas you were a business major for a couple of years and during your childhood played some sports or you're also a really big computer geek that can not only sketch and create a website design, but actually implement the code, test it against standards, and make a server backend, maybe even turn it into a business. Or maybe you or they are just so much more specific in their focus. Or maybe they don't have to have a day job like you do, or they've gone through 8 years of school. Maybe they rip off everything they do. Maybe you are destined to be the greatest designer of something so specific, like a typeface or something, and you're kicking yourself in the pants because you can't make a beautiful rose illustration on wedding invitation! Who knows. Point is: everyone is different. And everyone is good at something.
One thing that can prevent your confidence is comparison to others. It's my biggest thing, anyway. So abolish it, and get on with your creative, confident self.
Also, remember that failure is inevitable and a part of the process.