dw,ur not alone.
Even im a private candidate nd i do edexcel (int) AS chem,bio nd phy. It's been a struggle...My exams start on May 9th so yeee.....
I use PMT flashcards nd notes cz it makes it way more easier to understand the concepts. Then if u feel like the past papers are too new to u, try doing the past papers with the markscheme in ur hand so u get an idea on wat the examiner wants. Then eventually u vl be able to do the past papers without the markscheme. Conduct a mock exam nd focus on the areas where u hv gone wrong. This technique helped me alot so thought to share it to ya.
Even m really stressed out cz its my first time sitting for a board exm. I got straight A's for my igcse's so m desperate for gd grades this year too.
dw too much abt ur exams, im sure u vl do pretty well nd ur not a failure. U GOT THIS!!! GOOD LUCK!!