All students feel that, by asking something which is bothering them, whether their doubts or even some interesting things, they will appear stupid/unintelligent in front of others and, they stop themselves from asking their doubts in the classroom. The teachers too, during the class, ask students about their doubts related to the subject being taught in the class but students do not raise their doubts for some or the other reason. Almost every other student go through such situations, even professionals face such situations. Although, students should never let their doubts bother them when they can get an answer just by asking their teachers. Knowledge will be complete only if all your doubts are cleared.
You should always clarify your problems and queries from your teacher, as they too are ready to help students as and when required. Never let thoughts of feeling stupid or embarrassment hinder your knowledge.