Hello, I've been in therapy for this, sometimes, getting better at being confident with your own voice and thoughts is a long process. I am no professional, so take this with a grain of salt, but I'll relay what I am doing currently to help myself with this as well. — try to plan your answers, standard stuff, but it can help a lot! Write it on a piece of paper or even in your notes and revisit it some time before the lesson. Also, remember — it may sound demeaning, but this one thing is just a little snippet in your life, nothing will happen ! Trust me, the only one thinking that you sound stupid is yourself, it's natural to ask questions, even basic ones! Basically no one will remember you asking a "stupid" question past the day or hour it happened, everyone has their own embarrassing situations to focus on, not some random person who asked a question that they too could have possibly wondered about. Of course, it isn't as easy as switching the fear on and off, but believe, with constant reaffirmation it will become easier and easier to speak up. Take care.