What kind of belly fat is there? - There could be an adrenal/cortisol issue and working out may not be what you need at all.
Do you feel heavy all over or is this concentrated fat around the middle that seems to be an issue?
Really in a hormonal look - this could be something that could be ironed out for you. a few hormone tests - maybe a 24hr cortisol saliva test and you can get some answers as to why this isn't falling off too.
20 days of hitting the gym may not be something to judge your result on yet either... but you can sometimes eliminate hormonal issues as the possible culprit and get back to learning more on better methods on how to get rid of that for you.
It sounds as though you don't need to lose weight; just tone your muscles. Allmymarbles has a good point in regards to the way you carry yourself. If you make a point of holding your back straight, that will make it look like your stomach is not so large.
Additionally, there are exercises you can do to tone those stomach muscles. You could try yoga -- that tones muscles all over the body!! Also, holding the stomach in, will help tighten those muscles.
Watch what you are eating; there are foods that seem to make belly fat worse, as well as some medical conditions.
I just thought of something that used to amuse me. I lived in an apartment house with a very slow elevator. I would see people come back from jogging and wait for the elevator to take them up only one floor, when an open, wide staircase was just beside it. Is this something you would do?
Yes, you exercise, but how do you hold your body when you are not exercising? My husband is a very active man and has always had a pot. When he sits down he leans back and collapses. Thee is no tension in his body. I try to get him to sit up straight in a chair. He doesn't. Check your posture and become conscious of what you are doing with your body when you are not at the gym. Only a very short part of each day is spent there.