Hi, Mikeey. If you Google "soluble foods list" you will find lots of lists giving you soluble foods to choose from. I looked it up and, yes, sweet potatoes are on the list of soluble fiber foods that help ease constipation. So that's good for your situation. I would not eat the skin because it could cause constipation. Peel the skin, and eat the inside. Maybe later when you feel better you can eat the skin.
Livestrong.com is one site that is easy to follow and search. Also, if you want to know the amount of fiber in the food you eat, try "Fatsecret.com" you can search any food you can think of, and it will show you a complete break down of calories, carbohydrates, fat, fiber, sugar, sodium, vitamins, per serving. Five grams of fiber per serving is considered good. However, Fatsecret.com doesn't tell you if the food is soluble or insoluble. You will need to click on the soluble foods list to see that.