Re: Am I a terrible drummer?
I'd say you haven't played long enough anyway. After you've done ten years or so (for some even 20) you should be able to get a handle on whether or not you can do what you're supposed to do. 2-3 years just isn't enough for me to be a judge.
That said, band directors aren't perfect people either, so there may be some legitimate gripe he has too.
Or, like has already been said, you're messing with the parts you should be playing. I say post a video of your playing and then we can be the judge.