After my pregnancy, i've gained a lot of weight especial my belly is too big, what will i do to reduce my belly fat. should i stop using a depo?

Basics: You lose weight by consuming less calories than your body burns off/day. A bulging belly is likely the result of looser abdominal muscles that stretched out during pregnancy. Fat excess attaches to internal organs like the intestines when it doesn't stay outside. You can firm the belly with specific exercise & try a low carb diet. A visit to a nutritionist can help you get started.

Maybe. Maybe not.: A primary care doctor can help make sure periods are regular and nothing unusual is going on, such as a hormonal problem. One can avoid carbs (sugar and simple starches) because they increase the belly fat. Losing weight means eating fewer calories than one's body needs to burn each day. It's all math. Calories used up MUST be more than calories taken in, even in cases of hormonal problems.