Sir sometime i feel blank i can't think anything what smptoms are these?

Lots of possibilitie: This type of symptom is vague. It is seen in seizures, sleep apnea, attention deficit, thyroid deficiency, depression to name a few. Check with your primary care doctor to be evaluated.

Misunderstood words: These are a couple of the symptoms of going past words you did not understand when you were studying. If you find the words and look them up in the dictionary so you understand what they mean in the material you were reading or studying the symptoms disappear.