Why can't I ever focus properly and feel so dumb sometimes when it comes to taking a exam?

Personally i have test related issues as well. Sometimes i tend to overthink and second guess myself. You are not dumb by any means. Relax and breathe

Classrooms and exams are not suited to the strengths of all people. Some people find that they might excel at tests, while others are better at essays, and still others might be prodigies in completely different areas, such as art or music, that can't be tested by an exam. Don't get upset just because exams may not be your strong suit, just remember that your strengths lie in other areas.

Your lack of focus could be caused by a plethora of things. It's possible that what you're studying does not interest you and it is therefore difficult for you to focus. If this is the case, the studying you do may not be productive and you may not fully know the information you need to take exams. It is also possible that you have exam anxiety. If you get anxious during exams, you may forget information you learned while studying, resulting in your feelings of inadequacies. Lastly, you could have an attention-deficit issue. This would result in a lack of focus and unproductive studying, again resulting in not knowing answers on exams. The only way to know for sure which of these are causing your issues is to consult a professional. They may choose to do further testing or provide you further guidance, at the very least.

This phenomena is called "EXAM FEVER" :P I had this problem, since a very looooong time. It's like, I can happily study all year, I remember everything, I can solev all mathematical problems in seconds. But during exam time, I am the stupidest person in this world. I failed a lot of exams because of this. Meditation really helped me, maybe you can try that too.