It goes away over time and with experience. As you become more situated in your current company your confidence will grow and you'll become more productive. 'A

It goes away over time and with experience. As you become more situated in your current company your confidence will grow and you'll become more productive. 'Are you contributing enough' is a less important question than 'are you passionate about the field and do you like what you're doing'. If you're just in it for the money and uninterested in learning that'll make it much harder to reach a higher level of productivity.