Your - 4.00-dioptre lens power should not increase now. As you have stopped growing physically, the eye stops growing as well. You may wear spectacles but contact lenses should be better if you play sports or hate wearing glasses. Even if and when you get contact lenses, you still need glasses, as contact lens cannot be worn all the time. Laser surgery is possible but results can be unpredictable.
It is true that incidence of retinal detachment is higher in myopes but yours is only small power and should not worry much about that. Just get your eyes checked at least once in two years. Keep the computer at arms length to reduce the strain on your eyes.