Doc help me i don't know why i'm always weight gain even i on diet i eat less salty foods sometimes i eat small portions of sugar i do not drink sodas?

Too much l: this is a very frustrating situation. Many people are in the same building your caloric intake, and it is very frustrating to many. The best advice I can give you is to discuss this with your physician

Diet is not: enough you also need to exercise. Are you consuming 500 calories less every day than your usual calorie intake? Have you had your tyroid gland checked. Underactive thyroid is one of the cause of the weight gain. Discuss with your doctor.

Nutrition & exercise: Don't go on a diet b/c that's only temporary. Instead, focus on changing your lifestyle. Check out DASH & Mediterranean diets (yes, I know what I just wrote) b/c they're proven to lower risk for many chronic diseases. And they're free! Avoid sugar at all costs if at all possible. Then start exercise program. Just a little bit each day. Aim for 30min/d leading to 500kcal/d deficit or 3,500kcal/wk.