Many students who lack confidence in class would sound move confident by simply playing louder. Try 10% louder to start. Another take on fake it to 'til you make it.
Secondly, crescendo when the melody rises and diminuendo when it falls, unless the composer or arranger says otherwise.
This should help shed some of the timidity in your playing.
You've got to learn your instrument. Then, you practice, practice, practice. And then, when you finally get up there on the bandstand, forget all that and just wail.
I'm a professional pianist and music educator in West Toronto Ontario. I'm also a devoted student and teacher of the drums.