I'm glad your incision is healing well, Arella Mae. The change in your meds should help a lot in terms of how you feel.
You really don't need Gatorade or any of the Powerade drinks, and you don't need to keep loading up on fluids either--in fact you shouldn't load up on fluids, too much is as bad as not enough. Your dehydration was a few weeks ago, and it was due to the bleeding and vomiting and diarrhea, and it would have corrected itself as soon as you took in enough water and salt. Your body should now maintain its electrolyte balance and fluid balance all by itself, without your doing anything special. Just eat a balanced diet, with fruit and veggies, keep taking your vitamin pill, and drink about 6 glasses of water a day.
Why aren't you eating much solid food? You may not be getting enough protein--you need at least 45-50 grams of protein a day (meat, fish, dairy, eggs) to help keep your stamina up, along with carbohydrates. Boost is not that high in protein (it's about 12-15 grams a bottle, depending on which type you're buying). If you're really not eating much, try the Ensure high protein type--it comes in a 4 pack, the bottles are larger than the Boost and each one has 25 grams of protein. If you have at least one bottle a day, with some solid food and some additional sources of protein and carbohydrates at meals, you'll be taking in a more adequate supply of what your body needs to maintain your energy level. If, for some reason, you can't manage solid food, or your appetite is poor at the moment, drink two bottles of it a day.
Just eating better, along with the change in your meds, should really help you to feel less weak. And not taking in a lot of fluids, and drinks with sugar, might help your appetite return to normal so you can eat more solid food.
Definitely ditch the Gatorade/Powerade. You don't need it.