After 10 years of struggling to find answers for my GI symptoms and sudden consistent weight gain (100+ lbs), my Dr and I have run out of ideas to explore…

Personal Info:
22 year old female. Currently taking 125 Mcg levothyroxine (Hashimoto's) , 100 mg Zoloft (Anxiety)

Medical Background:
Around 6th grade severe GI issues began to emerge leading to cramping and severe diarrhea after meals, sometimes not even allowing me to finish eating. I absolutely cannot "hold it". At age 17 I had a colonoscopy and biopsies taken which revealed no obvious causes for the GI symptoms. During college (sophomore-senior year) I gained over 100 lbs even while maintaining an active lifestyle walking/biking and working a manual labor type farm job and occasionally going to the gym. This weight gain was initially blamed on starting antidepressant medication (Prozac) but did not subside when medication was switched and/or no longer used. 2 nutritionists stated my diet was not to blame for the weight gain either. In addition, GI symptoms are now even more prominent and include frequent heartburn. I have gone through several elimination diets to narrow down possible food causes of these symptoms, none so far have brought much (if any) relief. So far I have avoided gluten, dairy, cane sugar, processed sugars with no success. I have been tested several times for Cushing's (negative results) and my thyroid panel is within my normal range.