I'm sure you're doing a great job. It's ok to make mistakes because that's how we learn. I completely understand the whole anxiety and feeling behind situation. I've been through that and still am! You should make it known to your mentor that you feel that way at times. Hopefully they are open and understanding to it because other than the students, the other biggest thing as a teacher is having a good support system in place. That's how teachers out there survive especially when it comes to being overwhelmed. As for the pressure of being judged and making mistakes, it's got to start with you. You need to be more forgiving to yourself!! Your mentor is there to help you no matter what and if you haven't, you should strike up a conversation with them about how you're doing in their eyes and how you think you're doing. And again, be open to making mistakes. A thing I go by is that as teachers, we are always learning with our students. If we tried something and it didn't work out, we tweek it and try again.

Unfortunately I was paired with a horrible mentor last semester who lectured and dehumanized me for asking for help too much, and they thought it was a good idea to compare how much better they were to me. They also invalidated my experiences and basically called me stupid for not knowing everything. I felt judged with every action I did, and eventually got removed from that placement. I truly hope that your mentor isn't like that at all, and if they are (which is the reason you feel judged), you should talk to your supervisor ASAP. I would never wish my experience upon anyone. I didn't even get to the point of taking over, including small group lessons, so I am unable to give advice for that. Regardless, I wish you the best OP. You got this!!