Short gut syndrome

In 2019 I had two small intestines surgeries now I only have about two ft. of my small intestines left I still have my large intestines. My biggest problem is with dehydration and constipation. My body doesn't absorb enough fluids and that causes constipation. I have tried electrolytes drinks but they don't seem to help much. I started drinking coconut water with a little fruit juice in it and that seems to help better than Gatorade drinks. One of my GI specialist said that my fluids need to have sodium and glucose (sugar) in them for my body to absorb enough fluids. My doctor isn't helping me much with my dehydration and constipation problems. My doctor is wanting to treat my condition as IBS which I don't have. My doctor doesn't want to treat me for my short gut syndrome. Treating me for IBS makes my short gut syndrome worse.
I am able to drink and eat most things. No high fiber foods or corn. I have a difficult time gaining weight. I am having a hard time drinking more than 20 ounces of fluids a day before I get nauseated and start vomiting.