Such low myopic correction is unwarranted. Young persons have wide range of amplitude of accommodation. Your primary complaint when you were prescribed glasses is related to excess near work. A student or a computer user in addition to spending time on computer, spend time on mobile for work/ entertainment, adds to the eye strain due to excess accommodation.
Next Steps
stop using glasses. stop using mobile for entertainment. minimize computer use. Use hard copies to read if you are a student. if you are working, use bigger screen, keep it at I meter distance, spread/ stagger your work. 40 to 45 minutes
Health Tips
read "Ergonomics of computer use ". Modify your working habits. follow standard visual hygiene principles.