Absolutely not. As you gain domain knowledge you should feel exactly this way. I'd suggest that you be concerned if you didn't feel this way. When I finished highschool I thought I was pretty damn smart and had a lot of things figured out (clearly not the case). From an academic point of view as I worked towards my Ph.D. I was constantly reminded of how very little I did know. While I did learn new things day by day, my appreciation for how much I didn't know grew exponentially. In fact I think what I'm left with after the whole exercise is not a confidence in my knowledge but rather a confidence in my ability to learn, problem solve and ask questions.