Good evening
Walking in cloudy days will not help you as much as sunny days
Sun rays will effect your body to produce
vitamin D
so see that your body gets sun exposure at least for half an hour even in your house balcony
Next Steps
If u want detailed diet plan for increasing vit-D level consult me online through practo
Health Tips
use ksheerabala or Vit-D capsule , but don't use both at once