Welcome to the forum amd congratulations on having your surgery. A lot of gas is normal and will get better eventually. You can take Gas-Ex or a gereric equivelant which is MUCH less expensive. Gas-Ex will help but not totally eliminate the problem. You can also have have lactaze enzymes if you are lactose intolerant. Since you are 2 weeks post-op you should be close to starting the next phase of your meal plan and should start feeling less hungry once you do. Protein will curb those hunger pangs so try protein shakes. Just sip them very slowly and try thinning them out a little with some water or milk if they seem too thick for you to swallow. Being nauseous is also normal but if it is happening all the time you should call the surgeon. There are a lot of people on this forum who have problems with water and did better with warm beverages and protein drinks. You absolutely MUST stay hydrated or you will find yourself in the ER on IV fluids. Ounce for ounce protein drinks, Jello and popsicles count towards your fluid goal (low carb / sugar free).
The lack of energy is normal and is happening because you are healing from major surgery, losing weight and consuming very few calories. Your energy will start to come back in 2 or 3 months depending on your age, general health, diet and how much rest you are getting. Make protein your priority, shoot for 60 grams a day minimum in order to heal properly, gain strength and energy and to keep from losing organ and muscle tissue. And you MUST sleep and take naps as this too will help you recover much quicker.
Make sure to come back to the forum to let us know how you are doing.