Seems Moses didn't believe in himself either.
Echoing what Sub said -- I might be wrong, but I can't recall a single incidence (Moses, Gideon, Jeremiah, David, etc.) where God told someone, "Just believe in yourself. "
Rather, He told everyone He ever called, "Believe in ME." (Gen 15:1 -- "Do not be afraid, Abram, for I am your shield, your very great reward.")
I think this is one of our biggest challenges as Christians right now -- the world holds rallies, parades, and celebrations of SELF-affirmation (making us our own god,) but the one true God asks us to affirm our belief in HIM, rather than ourselves.
Proverbs 3:5 -- "Trust in the Lord with all your heart, and lean not on your own understanding."
I struggle with this, too... Stepping out simply because God asks me to, not because I feel like I'm going to ace the test. It's really a fight to look past our limits and see God instead, which is something we all wrestle with.
Blessings to you, Ben! May God give you strength in what He wants to do in your life and peace as His son whom He equips according to what He has called you to do.
Please keep us posted on your journey. 🙂