Why cant doctors figure out whats wrong?

I am 19 years old and have had gastro issues since 5. It started out as just stomach aches and grew to diarreah and nausea. Since january its vomiting now, too. Ive had gastric emptying study, ct scans, barium swalllows, multiple upper and lower endoscopies... the works. I was falsly diagnosed with celiac. I had an ibs diagnosis for years but medicAtions didnt help but rather made it worse. I was on reglan through iv at one point and it was terrible because i dont need to be sped up. Pretty much at this point i just had a ct scan with fold prominence and wall thickening but my new gastro dr doesnt think its crohns ( my dr in the stAte i just moved from thinks it is). shes stRting all the damn tests over again im really upset about it. My symptoms are diarreah ( mostly after eating) pain above the belly on, nausea, vomiting, & weight loss. its Dehydrating me to where im constantly getting ivs and kidney stones. does anyone have similar problems? I really cant live like this anymore