Five years of study---mmm. Does your "keyboard" have a weighted action. The better models will have a weighted action. What is your warm-up routine? Do you do scales, chords, arpeggios, etudes, and stretches? If your LH is weak----more scales---stretches---and work on the LH first everyday. You cant blame the instrument for our weaknesses---it is us that are weak. maybe you have out-grown your keyboard and need a better one----they are out there and available.
Kitty on the Keys