Eat small meals more often. In simple terms, eating spurs your metabolism — the process by which your body turns food into energy. Eating more often, then, may kick your metabolism into a higher gear more times per day (e.g., if you eat six times a day, you get six “spikes”). But, you must make sure that eating more often does not also mean eating more; it's essential that you reduce your overall average daily calories.
The combination of exercise and healthy foods & drinks obviously cannot fail. Better yet, it solves one of the main food-related problems today: the excessive consumption of soda (especially in the USA). For many people, it is the only thing they drink (instead of water). If you are like this, switching from sugary sodas to red tea alone makes a huge difference to your body. But then you also detoxify it, so the effects are even greater.
Maybe you are trying too many things. If you keep switching diets and are doing too much exercise, your body is trying to balance itself. it might also be caused by lack of sleep or too much stress. Do moderate exercise and start eating a little bit cleaner and the pounds will come off. If you still don't notice a difference, talk to your doctor. You might have a thyroid problem or some other medical issue.