Speaking from personal experience, you may never feel like you're 100% ready, but that's okay! The best advice I have is to focus on taking multiple PRACTICE EXAMS. Try your best to simulate testing conditions (i.e. time each section including the 30 minute break in between, use an online calculator, etc.). There are a lot of factors that play a role in testing ability that you don't really think of. For instance, I scheduled an 8am OAT, so I took one practice exam at 8am to see how the early morning would affect me.
As for the last day before the exam, I'd suggest not overexerting yourself - maybe just review any formulas/o-chem reactions that trip you up the most. Make sure to sleep really well the night before and to eat a healthy meal beforehand. You've studied for a few months now, so just approach the exam with a confident mindset (positive mind = positive outcome)! You've worked hard, and the results will surely reflect that!
Best of luck!