Is my supervisor making things clearer or confusing? I am struggling a lot these days while presenting in front of my supervisor. I make many mistakes, sometimes very stupid mistakes, and he is now saying, "You need to avoid these mistakes." I am not able to focus on theorems, lemmas, etc. but instead focus on things like how to avoid mistakes in front of him. Many times I feel nervous in front of him, sometimes sweating in front him due to nervousness. Although he tries to make me calm but also give strict feedback. 

The one question that makes me worry is that he knows the things I am presenting in front of him, but he doesn't try to clarify things. To me it appears that he creates confusion in the proof that I try to present.

Question: Is my supervisor making things clearer or confusing?

On the comment of @Magicsowon I am going to add a detail here. When I discuss things with him he asks, "What is this?" Now the problem is there can be multiple definitions of the same term. Then I often assume the wrong one and do the proof. In the literature I follow, things are not defined in a good way so most of the time it happens that there is a confusion on concepts.
When and why would I, as a supervisor, ask students "What's this?" rather than just telling them (assuming that "this" is something I already know about)? The most likely situation is that I can't tell whether the student understands the relevant definition. If I already knew that the student didn't understand the definition, then I'd explain it, but if I'm unsure about the student's understanding, then I might ask questions intended to show me what the student knows or doesn't know. The student might view such questions the way you did, as "making things doubtful", but that wouldn't be my primary intent. (It might be a good side effect; if the student has a wrong idea, causing doubt about that idea might be a good preface to explaining the correct idea or to sending the student to study it.) 

I'm worried by the last part of the material you edited in at the end of the question, the part about multiple definitions of the same term, assuming the wrong definition, things not defined in a good way, and a confusion of concepts. This sounds like a recipe for a disaster. I would recommend that, as soon as you see two genuinely different definitions of the same term, you try to determine whether they are equivalent. If they aren't, or if you can't decide whether they are, then ask your adviser to explain. Are there really two different concepts with the same name? If so, which interpretation of the name should you use? Getting the definition clear is necessary before any other work involving that concept; anything built on unclear definitions will be unclear (if not outright nonsense).