Hi Starmissy. I'm not a doctor, I can't diagnose anything. Based on the symptoms you describe it seems like a real possibility that you might have celiac disease, I think you should pursue a diagnosis, or ruling it out, with your doctors.
You mentioned that there are family members with diabetes, if this is type 1 diabetes, a/k/a juvenile onset diabetes, that is an autoimmune disorder as is celiac disease and people with one autoimmune disorder are at increased risk of developing other autoimmune disorders. It also suggests the genetic presence of susceptibility to celiac disease in your family.
You mentioned that your sister has been diagnosed with IBS, this is a catch all diagnosis used when doctors do not know the real cause of persistent intestinal problems. It often happens that people who have been diagnosed as suffering from IBS are later discovered to have celiac disease.
When one person in a family is diagnosed with celiac disease the probability that other family members may receive the same diagnosis goes up enormously as compared to random members of the public.
Very much of what you say does sound like celiac disease to me, but please do get a medical professional to give you the final word.
