Do not get demotivated by your failure. Failures are the part of success. Learn from this failure and dedicate yourself to crack the IIT JEE exam.

For being eligible for JEE Mains 2020,then you have to pass the 12th exam which you will be giving in 2020. You not only have to pass it,but have to score more than 75%. Then only you will be eligible to make your dream come true.

Other than this, I will suggest you to fill the form of NIOS (National Institute of Open Science). This exam is equivalent to your board exams and the best thing about this is you can give exam at anytime of the year. Score well in this exam and you will be eligible for the JEE Mains exam.

Feel free to ask me in the comment box if you are having any further doubts

hope you find it helpful

Good Luck!