JEE mains is one of the most exams of your life firstly please don't panick, you can make it this time. Firstly in Physics positively read SHM , gravitation, all the sums of vectors, Semiconductors , electricity and in chemistry don't skip the s,p,d,f block elements, organic chemistry basics. In math prepare yourself well in Differentiation, Integration, Limits , Binomial Theorem, Arithmetic and Geometric Progression.

Good luck and it's your time !!!