My stool is yellow why is that and constipated i have a really bad diet and can it be from sugar and not eating veggies?

Try high fiber diet: It is important to have proper diet. You are young and it is good to get into the habit of eating right. Diet high in fiber which includes daily servings of fruits and vegetables is important. Oat bran cereal, wheat bread, quinoa etc. Are also high in fiber content. Diet rich in meat alone does not give one enough fiber.

Vegetables: Eating more fruits and vegetables can help with your constipation cause they contain fiber. Having processed sugar and flour in your diet and other processed foods have little to no fiber and contribute to constipation. Try to eat half your plate as vegetables. Beans are also a good source of fiber and try to have about a gallon of water a day- to make sure the fiber and fluids make a soft stool.