it would not be possible to specifically address your question as to why your vision has deteriorated over the internet. we do not know anything about you your medical history your age or have any way of examining you so you will need to see an eye care professional such as an ophthalmologist.
developed myopia over 4 months and i can't read a sign until i pass it. weak prescription fixes completely though. why? . i had perfect vision for years until 4 months ago. i realized i couldn't read the board a. anymore. then i noticed that i was also having trouble reading signs while driving. it was just reading at first though. i went to have an eye exam and i was told that i needed just a hint of correction. it corrected my vision. i now can only make out general shapes past 15 feet. beyond that everything is a blurry mess. my prescription still corrects it. how is that possible if my vision got so much worse?