Amblyopia develops during childhood around the age of 6 to 11 years. It might be that you have just noticed it. Even if you have amblyopia which you have noticed now, it is unlikely that it will progress in 3-4 months at this age. So, this is not the diagnosis.
Next Steps
Please have your eyes and vision checked in person. You would require a dilated retinal examination as well. painless rapidly progressive vision loss in one eye , you need to rule out retinal problem.
Health Tips
Do not ignore, consult in person locally.