There are many reasons you are feeling this way. You are not alone. The time preparing to take your boards is a strange time in your life. It can be very intimidating. There is a lot of pressure. But you can handle it! Everything is going to be okay!
Take some time and get away from studying. Spend some time with friends and family—take your mind away from the boards. HAVE FUN!
When you are ready to get back to studying think about these positives: you succeeded on your MCAT, you got into medical school (which is truly the biggest step!), you have passed medical classes that the average person wouldn’t even begin to comprehend, you have dissected a human body (and only got nauseas twice!), and you are going to be a doctor! You are going to help thousands of people in your life!
So relax, think about the positives, and remember this is a marathon not a sprint. Take one day at a time and you will be successful!