Dear amaaniz,
You do not mention your age. Age can play a role when the prescription changes. There is also some evidence that near vision tasks may also play a role as there has been a 41% increase in nearsightedness compared with twenty years ago.
Dr. Feldman
Sandy T. Feldman, M.D., M.S.
ClearView Eye and Laser Medical Center
San Diego, California
My age is 14 ....i turned 143 months ago on 14th December