Glasses with wrong strength should focus the incoming light wrongly and therefore effectively blur things.
If you can, I'd recommend trying out someone else's glasses. It can give people headaches when their vision is blurry, because they'll try to focus their eyes really hard.
You know what happens to the glasses that used to work, but no longer do because your eyes have changed? People archive them to the bedroom drawer just in case someone like you might one day show up. Ask anyone who wears glasses for an old pair they haven’t worn in the last decade. Usually, you get to choose from several options.
BTW, the headache thing is real, but you’ll learn that soon enough.