According to your sign and symptom you are suffering from constipated stool.
Hard and pebbles type stool means your water intake low and
You don't fibrous food.
Color for stool is depend on multiple factor-like- type of food intake,
Any malabsorption problem around the git area.
Next Steps
You should first improve your life style.
You should take plenty of fluid like 4-5 litre water per day .
you should take less spicy and fatty foods.
You should take fibrous food.
If you will not improve then do test
as CBC and ESR and
LFT and
Lipid Profile and
Do USG of Whole abdomen.
Health Tips
Please follow good life style as take plenty of fluid and take less spicy and fatty foods and keep positive attitude to fight any problem of your life.