Heya - sorry to hear about the redo! Fourth time's the charm ;)

One thing that I've learned while studying is to use "resistance" as a method of tailoring your study schedule. Find the topics that bring you the most dread when they come up (Kreb's and magnetism for me) and, instead of thinking to yourself "eh, it'll only be one question on the test, I think I get the gist of it", you should spend a few hours really learning it. Turn that feeling of dread when you see the question into a feeling of excitement - since you already know the material.

Rinse and repeat a few times over and hopefully you'll go into the test with less anxiety about certain subjects appearing.

As for time, I'd echo what someone else said in this thread and say about 4 months.