Hello and hope you are doing well.
It could be a gall bladder problem with you symptoms of right quadrant pain, vomiting and loss of appetite. Ultrasounds and CT scans will help detect any abnormalities in the structure of the gall bladder. To study the functioning tests like HIDA scan need to be done. Gall bladder dysfunction can cause intolerance to fatty food. The other causes could be due to gastroenteritis, malabsorption syndromes, diverticulitis, Chron's disease, ulcerative colitis and parasitic infections. In addition you seem to be having constipation. If the other pathologies can be ruled out then there is an entity called Irritable Bowel Sydrome (IBS). Once a diagnosis has been confirmed then an appropriate diet schedule can be planned. Discuss these options with your doctor when you happen to meet him next time.
Hope this helped and do keep us posted.
Oh good luck with that appt and do keep it if you can. Please come back and let us know how you are. Your story sounds like my daughter when she was 17 and it's been a few yeas and without her gallbladder she's doing fine and her reflux is next to none. I have gallstones and have been in remission for a few years, but I know that pain all too well, too.