How long have you been studying for the exam? If you've been at it a while, then burnout is all too likely. With almost four months to the June exam, you might benefit from stepping away from the test for a couple of days and coming back to it with a clear, relaxed mind.
Whatever you do, don't let this test defeat you. Just relax and regain your focus. This long before the test, try not to force yourself to do too much work if your mind isn't letting you. Otherwise, you're potentially wasting material.
Give us a little more information (e.g., how long you've been studying, how you're normally scoring in general) and we could probably give you a little more reliable advice.