The first thing I would do is set realistic goals - going to an a is very tricky but aiming for a b is more managable in 2 months
The second thing I would do is revise
Make a revision timetable
Make notes for all your subjects and learn them
If there isn't anything you get go online and watch youtube videos
Do lots of PPQs
One source that I think will really help is seneca - if you do all the modules for all your courses will be really beneficial and can bump you up a grade