I think maybe you are just psyching yourself out for the boards. Look at it as a chance to prove yourself and how well you can do. It is necessary for your future.
When I have important things come up in my life, I like to meditate or quietly reflect on what the event means to me and how I can do my best at it. Take time each morning to sit and quietly think and reflect...this may help. I know it is hard with ADHD and I struggled in the beginning but with practice I was able to finally suceed. Good luck and I hope things go well for you