Yes, You will be able to see OMR sheet after JEE Main. Before JEE result is announced. You can see it online on the NTA portal around ten days after JEE Main Exam gets over. You can also estimate your score by cross-checking your responses with the original answer.

Hi Raul

The official website of JEE Main 2018 has been updated for JEE Main 2019 and as you must be aware that this year NTA has taken over CBSE to conduct the exam. Therefore, you may not get previous year information.

However, you can check the following link, if it helps:

http://cbseresults.nic.in/Jee_main_pzy/jee_cbse_2018.htm

All the best!