I really struggled in the first few weeks. I was told that it's very normal.
OB told me to check that my prenatal vitamins didn't contain a stool softener, and to make sure that anything I was eating was high in good fats (nuts, seeds, avocado, nut butters etc) to try and prevent me losing weight.
I had also been taking Magnesium for headaches which I stopped, scaled veggies and fiber intake back and tried to eat small portions of bland food. Lots of dry crackers, rice with salt and butter. Was also told to drink electrolyte water/coconut water/even gatorade rather than regular water to make sure I was getting that extra hydration. It eased off after a week or so but it was pretty awful for a while. You have my sympathy!