First of all you are 21 and i think you have much more to achieve so don't feel bad about it and about the low self esteem it might be due to your own negative thoughts so make yourself prepared for 2 days that you are going to study no matter what so that you will get prepared physically and mentally.

Never feel bad thinking about your parents as it always makes you feel under confidence., Always think that you are gonna make them proud so that it boosts your confidence.

Now, about the study cycle for the exams don't plan anything with lazy mood.Make sure that when you plan the study cycle you do it or else never plan a time table. Study the easiest topic possible so that you can build more confidence.

You can do it.

All the best ...!