We hope you are preparing hard for JEE examination in the best of spirits. As you mentioned, you have solved many questions from many Physics and Mathematics books. Why then are you not confident enough about the concepts?
Be confident. Ask your tutor or teacher or guide to help you out of this state of confusion, as it is very dangerous for your actual exam.
What we can say is, try to go for as many mock tests as you can. It will test your conceptual understanding. Focus on practice papers.
The top five benefits of solving mock tests for proper JEE Main Preparation are as follows-
It helps in Time Management
It familiarizes you with Real Exam Environment
It reduces the number of mistakes
It helps in Revision of Complete Syllabus
Boosts your Confidence Level
In the end-
Don’t just hang on with a single chapter. Some students try to go through four or five books for the same chapter. And finally, they lose interest in the minor chapters. Avoid that. Try to give equal time to every chapter whether it be small or big. If you find a chapter or a concept difficult, you can dedicate more time to practice it. But do not go through too many references as it will confuse you. Some students go through one book for each subject and that helps them a lot. One student, I personally know, revealed that he went through one book for each subject, but thoroughly.
We wish you very best for the exam!