If you think that you can't do this doctoral thing, it's okay. If you need to ask for clarification about things in class, in writing, or regarding administrative details, it's okay. If the image to the right is how you feel sometimes, it's okay.
As grad students, we all have to do this grad school thing for the first time sometime. We're all green at it until we're not. And as the saying goes...
it's not easy being green.