Having trouble with CFI

I've recently got my commercial ASEL and I'm now working on my CFI. I've now been training for CFI for about 2 weeks and I feel as if I thought I had a good grasp on most concepts in aviation and now I feel overwhelmed because now and I feel like I don't actually know the concepts. I've realized this when I started to practice teaching on my CFI and every question he asks me my mind goes blank. I am doing a lot of self study to make sure I know these topics inside and out but I still just have a hard time teaching. While I'm very motivated to become a CFI to be a good mentor to future pilots I start to lose motivation when I cant consistently answer the questions my CFI is asking me while teaching. Also Just to keep in mind I've never had issues with checkride an and I did well on my written tests. So I feel like I should know more. Is this a normal feeling to have? If any other CFI or pilots training to be a CFI has experienced this feeling please feel free to share and share any tips.