Im 20, i cant focus, have short term memory problems, fatigue, i feel weak or unmotivated, easily distracted?

Hi. I have theories about a condition i think i may have, but i dont want to make false assumptions and convince myself i have it, so im asking what it may be. Lately at work i havent been able to focus, my attention is drawn easily from tasks, i cannot pay attention to detail, and my supervisors are starting to notice, telling me im in lala land and that im somewhere else although my body is there. Im also feeling weak, almost like i havent slept. i sleep plenty, but not good sleep, or at least it doesnt feel like it. it almost feels like im detached from the rest of the world, living a life disconnected from the network of society. i always feel like theres somewhere else i have to be. im impatient, and i as much as i try to focus on my work, i cant. i feel like i could be so much further ahead if i could concentrate.im 20 years old, i quit smoking about 4 months ago, and i work nnight shift if it makes a difference