What you are talking about could be what is called "Brain Fog".
Symptoms...
* Loss of mental acuity
* Forgetfulness – decreased short-term memory
* A feeling of spaciness and inability to think clearly
* A feeling that you’re in a fog or a dark cloud is over your head
* Decreased attention span
* Mild depression and/or anxiety
* Lack of spatial awareness
* Difficulty concentrating or a lack of focus
You might want to look into taking some supplements for a little while.
Good luck, hopefully this helps!