I use a -0.75 eye glass but still can't see from a distance, should I change it?

Need new glasses. You most likely need new glasses, but you should be evaluated by your ophthalmologist to make sure there is no other cause for your blurred vision such as cataracts, dry eye, or many other causes.
Yes. Important to have them checked by an eye doctor. Very possibly correctable with a better eyeglass prescription, but you want to make sure that there are no other problems causing this.
Yes. If you do not see well with your current lenses, you should see an eye doctor and have your eyes examined and your prescription checked. It is not common for your prescription to change over time, but you should have an eye exam whenever you notice any changes in your vision.