The flab on your stomach is just a part of the flab which is all over your body. The people who are telling you you can't target it specifically are right; you have to just lose fat and your body will remove it from all over your body. So you should reconceputalize your goal as just "losing weight".
note that everyone has an inherited pattern of fat distribution. That means that when you gain weight, the fat tends to go some places more than others. By the same token, when you lose weight, the fat loss will come off in the same way it went on. If you tend to put fat around your stomach when you gain weight, then you'll tend to lose fat from your stomach first when you lose weight.
Losing weight is a game of numbers and you need to know them and track them in order to succeed. Here are the numbers you need:
1) Your resting metabolic rate. This is how many calories your body needs in a day to just exist- breath, sit upright and keep yourself alive without losing or gaining weight. There are ways to guess pretty accurately and there are ways to find out with certainity that involve specialized equipment. This is something for you to look into- trust *.gov and *.edu sites for accurate information; there's a lot of quackery out there.
2)The total calories in the food you did in fact eat during each day, every day. You have to track these scrupulously every day. You need a calorie counter which lists the actual foods you ate and you need an oz or gm scale so you can know for a fact how much of each thing you ate.
3) An equally accurate record of your calories expenditure over the day. There are three parts to this. One is your RMR as discussed before. That is the baseline number of calories you're guaranteed to have spent even if you're sick in bed.
The second part is the calories above your RMR you spent just tooling around, working and living life. This excludes exercise. You can accurately guesstimate these numbers by characterizing your daily life as sedentary (office job where you sit), mildly active (sitting for most of the day but with periods of walking or standing) or very active (being a nurse, say). Go online and find a trustworty site which takes your weight and height and your activity level and gives you back a percentage of your RMR (in calories) that your daily life requires over and above your RMR. There's of course an app for this too.
The third part of the calorie calculation is the calories you spent deliberately exercising. Again there are .gov tables and tables from various .edu sites which have been assembled using thousands of test subjects over decades and you should find and use those tables. They are accurate. Be careful with apps not all of which may not give accurate information. It is very important that you're numbers are accurate.
Your RMR is generally fixed and unchanging. The calories and exercise are numbers that vary and you have to track them both every day. You should write them down as you eat them in and exercise them off.
Now that you know what numbers you need to track on, here's what you should do with them. You should make sure that you're consuming 500 fewer calories than you're using each day. That is a high goal to achieve, but it is effective and realistic. It will result in the loss of 1 lb. (2.2 kg.) per week (1 lb of fat = 3500 calories; 7 days of the week x 500 calories a day = 3500 calories).
At that rate it's unlikely you will even have to diet 20 weeks.
So starting with your RMR, add the calories from your dialy life and the calories from exercise. That is your daily caloric expenditure. Now try to adjust your calories from food, so you're 500 calories short of what you expended.
This means getting to know how many calories are in any serving of food that passes your lips. That means weighing or measuring the food, looking up the calories and writing it down. Pretty soon you'll be an expert in calorie count for the foods you regularly eat. You have to do this.
It also means truly knowing how many calories each exercise you do burns per minute. Some burn more than others but you can't do them for long- i.e. weightlifting. You only count the minutes you are actually exercising, not the time you spend between sets or standing and breathing hard or anything else. Mild aeorbics doesn't burn as many as weightlifting as a rule, but is better for losing weight because you can do it for longer than an anerobic exercise like weightlifting. It just amounts to more calories burnt!
You have to be a little OCD about counting calories and exercise records and you also have to be realistic in your goals. In the beginning, really the first week or so, just counting calories and accurately tracking exercise without trying to limit your food intake is quite enough discipline to have to adjust to.
The second week, try limiting your food so you come in 250 calories under what you calculated you used. You'll feel real hunger there and you have to teach yourself to cope with that real hunger. I would say a couple of weeks of being successful at that is a real milestone many people fail.
Now you're aware of how long you have to exercise to burn off a banana or a piece of toast and you're looking at those foods differently, thinking things like "if I eat this, then it means another 15 minutes of cardio, and that's a lot of work!".
The third week you can step things up so you're realizing a deficit of 500 calories. Don't think this is easy- it's truly hard dieting, but not so hard it's undoable. The chief reason people fail is, well, they don't know to do any of the above, LOL but for those who DO do the above, the chief reason they fail is they get greedy and try to go on too hard a diet and because food supplies the energy needed for willpower, they run out of willpower!
Really a 500 deficit is full gallop and will get you anywhere you need to go in excellent time.
One other thing- exercising the area you want to lose fat from doesn't work. Specifically, exercising your abs to lose fat around them doesn't work. The energy your body needs to do exercise is not drawn from the fat stores around the muscle you're working. It's drawn from the energy (glucose) in your bloodstream as a result of your last meal OR it's drawn from adipose tissue evenly, from all over your body.
You cannot induce your body to lose weight around your stomach by doing exercises for your stomach. Just lose weight, and the adipose which is covering your abs will shrink in size then, as a consequence, you'll then see the ab muscles clearly, muscles you always had, but were hidden under fat.
Very best of luck to you!