Related to mind and brain. Material.

Sleep is a very important biological function. As you have mentioned, you try to substitute your night time sleep in the afternoon but you havnt mentioned if it is deep, comforting and refreshing, as that may be one cause of your headache. Secondly, including regular exercise like walking shall help you both physically and mentally. That said, kindly get an eye check up done to rule out any such causative factor. Shift jobs can have a negative impact on the normal biological rhythms, and can also lead to impaired concentration and negative emotional states. I would advice you to seek psychiatric consultation to rule out other mental health related disorders which may lead to such condition. Hope this helps you..