Mental fatigue. Night just like that.

I woke up one day and didn't feel right. I felt like I was sleep deprived. That disorientating feeling of not being able to fully process things going on. I was sleeping fine and was getting enough good quality sleep. This was 3 months ago and it's still an issue. I feel barely awake, it's like my brain isn't working properly. I can't properly look at things and take them in. I can see them fine but it actually hurts my head to try and focus on an object. My head just hurts and feels tense when doing the simplest tasks. I just can't feel normal. I used to feel extremely awake and energised. But this feels like a filter has been placed over myself and it's horrible. It's so hard to explain, but it can almost cause things to not feel real sometimes. I know they are but my mind is so tired it's like being sleep deprived when you are just too tired to process and work properly. But that's how I feel all the time. And it's just strange how it came on over night just like that.