One possible cause is astigmatism. Though there might be other general causes as well, such as dietary deficiencies, lack of adequate sleep, ENT problem etc.
Next Steps
As far as astigmatism is concerned, kindly visit an ophthalmologist for a proper refraction.
Health Tips
If your screen time is high, kindly reduce it or give yourself screen-free times periodically.
Consult a specialist if you feel highly dizzy and are barely able to stand straight.