Gaining confidence in shooting can come from a few things.
When struggling with making shots - head to practice 20 minutes earlier (or stay later) and do what we call -"form shooting" - this consists of shooting the ball really close to the hoop, start with 1 hand and really concentrate on your form and technique - go through your progressions, then do your normal 2 hand shooting.
B - Balance
E - Elbow
F - Follow Through
Shooting is all about Rythm, Repetition (practice) and confidence, and every good shooter has bad days. Put some extra time in practicing if your struggling because that extra practice will help you gain back your confidence.