As a member of a football club I can tell you from experience that exercise does not equal fat loss. Your real problem is that you consume too many calories and they deposit themselves around your belly leading to an "unflat" belly.
Fat gain is a stress response, a defense mechanism of the body. The body will store energy as fat so that it can use it in case of an emergency. If you are unable to loose your belly that is because your body is under stress. Let me clarify. We are not talking about mental stress or emotional stress. It is physical stress.
This stress on your body is caused by eating the wrong things. In order to reverse the negative effects of eating starches(pasta, bread, pizza, potatoes...) and sugars (sweets, fruits, cakes...) as well as all of the junk that is in processed food (the unpronounceable ingredients) you must avoid them.
Not eating them is hard when you crave these things. In order to stop craving them, supplement with whey protein, amino acids such as L. Arginine and L. Carnitine, Iodine and sufficient absorbable vitamins and minerals. Also, make sure that you are able to absorb all of these things. If you have digestive problems after eating fats then you know that you need to correct them. Cod liver oil or flax seed oil or Coconut oil are all good fats which are necessary to be healthy, eliminate stress and to lose fat.
PS. There are good fats and bad fats. Look up Udo Erasmus. He work the book about fats.
Simple eat properly and avoid foods that burn sugar instead of body fat. All processed food is poisonous. Do not eat breads, pasta, race, potatoes, cooking oils, starches, grains. Only drink fresh water not soda pop. Do not eat snacks like chips, crisps, and other treats that are prepackaged.