Sounds like you don't have a handle on their progress, that always makes me feel panicky. Do they all have targets? Writing targets, maths targets etc so you know exactly what they have to achieve to hit the next sub level? And do you have a really up to date assessment folder?
Also, do you have control over them all the time? I find that if I feel like my control is slipping, lots of other things slip too like behaviour.
Eg I wait till every child is looking at me before I start teaching. I wait for every child to be standing behind their table at the end of a lesson, wait for them all to be silent when lining up to go out to play/assembly/lunch etc.
I also use lots of visual communication, and model the behaviour you want them to do eg folding arms so they do, sitting up straight etc.
And I wouldn't worry about your mistakes, my class love it when I make a mistake!!! Hope that doesn't all sound patronising, I totally know how you feel and when it happens to me, I go back to basics and reestablish some of the class rules and go all strict on their asses!!!!!
But in answer to your original q, yes and no! Sometimes it feels amazing and I think I am brilliant, other times I wonder how I am getting away with pretending to be a teacher.
DH once wrote in something he had to send to someone; 'my wife is a primary school teacher' I actually did a double take and looked at him all bewildered, like what, is that me?!?