Hi there
This is a problem faced by 30 p.c. of IIT aspirants i feel.But u need not to worry.
As someone from goiit had earlier said that u can definitely achieve IIT when u are donating one complete year of ur life to it.
But u have to make it fast. I suggest that before ur school reopens after Summer Vacations try to be REALLY THOROUGH with ur class XI syllabus.Since u have not prepared ur concepts well for Class XI which is very imp for JEE i feel u shud to work really hard these 2 months atleast.
The next step is to join an All India test series like that of Brilliant / FIITJEE( i recommend brilliant) so that u can assess urself on how much u have prepared.
Books to be referred :
Physics:
1. HC verma (I and II) is a must.
2. Only when u are thorough with HCV then u must Buy DC pandey (i leave this choice to you).
Chemistry:
1. Our Nepali Hero......P Bahadur..Highly recommended.
2. RC Mukherjee...pls refer the solved examples.
3. For Organic u can refer NCERT ......and Morrison Boyd.
Mathematics:
1. ML Khanna,TMH or A Das Gupta.
2. SL loney fro trigo.
If u do atleast from these books DEDICATEDLY then u can definitely crack IIT with a very gud rank.