Suggest Medication For Irritable Bowel Syndrome

I have had gastro problems for years I am 24 and I have already had a colonoscopy they said IBS. Yet without having my medical records I don't know more than I was on a feeding tube for four months when I was a year and a half for being underweight and not digesting anything then. My doctor wants to test me for cystic fibrosis because I get greasy loose bowels almost every day and I have high cholesterol and I am insulin resistant. I don't know what is wrong with my stomach but I now have a related rash everytime I get loose bowels my face breaks out?? If it's a food allergy I don't understand because its not just wheat etc I get it from anything I eat lately, Food comes up my throat like I have acid problems but I don't get a lot of heartburn, My grandpa had a colostomy bag for fourty years and I wish I knew why but between diabetes being prominent in my family and what I am going through now I am stumped. I do get sick a lot as well with frequent sinus infections and bronchitus and have had to pancreatic attacks that has left scarring. That's why my doctor wants to test me for cf but I have no insurance due to losing my job a month ago. My question is what in the immune system can be failing causing a rash and greasy bowels? Is it possible it's my liver?