Is it normal for my childs confidence to drop when a teenager?

Difficult teens. The teen years are not just a problem for parents. Teens go through puberty at differing rates which triggers a lot of "am i normal" thoughts. They become self conscious about weight, clothing, hair, sexuality, money etc as their brain matures & they see the diversity in their friends.Significant anxiety occurs in up to half & many need third party counseling thru the rough spots.
Confidence. Perhaps it is: peer influence, including judgmental behaviors creates anxiety and self-doubt about almost everything a teen says, does, dresses, etc. Confidence improves with success in relationships, school work, and moving through the teen years. Don't forget to talk to your kids!