After gall bladder surgery there is no change in fat metabolism. If you are gaining weight it's most probably because you are eating too much. Go on a diet.
There are some diseases, certainly, that cause you to gain weight. These are rare. Therefore you should consult a physician only if you are convinced that your weight gain is more than mere overeating.
Gall bladder surgery does not cause heartburn either. You may need some medications for heartburn (e.g. pantoprazole and domperidone), so consult a physician or a gastroenterologist for this. Remember that heartburn is commoner among overweight persons than among slimmer ones.