thanks for query.
firstly you rule out thyroid
Seeing your profession you might have lack of physical activity.
Take less fat and carbohydrate
diet,more green veges and fresh fruits.
Nothing in between two meals except salads.
Go for exercise like walking,running,jogging and rope jumping.
To decrease fat from tummy do abdominal exercise
,In this exercise lying down on thr back,raise your one leg as long as you can keep it for few seconds,then another leg.
Then both the legs.Do this exercise 10 mnt in the morning and 10 mnt in the eve.
Then lying down on the chest and do same thing as mentioned above.
This will definitely help your tummy getting reduced.
ok and bye.