What Causes Headaches And Feeling Of Strain In Eyes?

thanx for this wonderful site i hope to get my awnser. female age 23 yrs, ht 5 feet, wt 85 kgs. My eye power of both the eyes is -5.5
No matter how much i sleep, still my eyes & head are always strained seems to be streched . headache is common. I thought my power incresed but tat was also not the case. And if i m watching TV, computer or m too hungry that streching feeling & headache becums worse. I try to keeep my eyes close as much as i can while out of home. thaxxxxxxxxx in advance