James, 

You scored 92.6 percentile in jee mains January which shows that you are pretty clear with you PCM topics. 

And recently you gave your board exams which means you don't have to learn those formulas again.  Those are quite fresh in your memory. So why are you afraid  

What you need is just practice you got 10 odd days.  Start practicing JEE MAINS last year papers.  Do at least 2-3 question papers daily. 

You will be in touch and you will gain speed and you will fetch good marks. All the best!!