I'm not sure if there are meds that can help a lack of self confidence. Are you addressing this through therapy as well? I used to have a huge lack of self confidence, and I found through therapy, mostly CBT, I was able to overcome these thoughts and I am quite a confident person today.

As for your last question, it depends on how often and how severe the downs are. Even normal people have periods where they feel down. Eliminating them completely is unrealistic. But if they are damaging your ability to function or are causing significant distress they need further treatment. You should talk to your doctor about this, we don't know and are not qualified to advise you on med changes.