Hello,
You seem to be having progressive myopia. This is when the minus power keeps on increasing with time. However, it tends to stabilize by around 20 years of age. But your's is increasing.
Next Steps
Do visit an ophthalmologist to rule out glaucoma. This is when the pressure of the eye increases, sometimes leading to increasing length of the eyeball, and hence minus power.
Health Tips
For the time being you may use eye drop Nepafenac 3 times a day for releaving pain.