I am an IBS sufferer for many years. It seems like yours is IBS-D and not C-constipation. Doctors didn't try any medications? IBS is a tough one to treat but there are ways to address them.
I tried the medicine DICETEL when I was in Canada and still take it when I need. It is not available in U.S and a prescription medicine. You can get the prescription from any doctor and get it from an online store in Canada.
Recently I discovered the probiotics Align helps me too and I stopped Dicetel. you can try that too and not a prescription medicine and available everywhere.
Anti-depressant drug Elavil (low dosage) work for many conditions besides depression and some people had success for IBS -D and I take 10 mg at night which keeps my stomach calm. Yes, anti-depressants and anti-anxiety medicines help but try to stay away from them if you can.
I also take another supplement LIV 52 which improves my appetite and helps with IBS. But you have to take the one which is in red tablet form and not the one in capsule.
I eliminated lactose completely and lactose sure is a problem for me. some people eliminate gluten too.
Bottom line you have to try out and i mentioned few and there are many other ways. If you doctor not helping go to a different doctor.
i hv really found out the real reason for i.b.s. , i am from biological background with maths and i turned out an engineer instead of doctor but i suffered from i.b.s. throughout my past life,see its a nuerological problem though it is considered as phsycological or physiological, pathogenic many times.now i go through detailed explaination ,it really is brain gut derailment,due to which there is little absorbtion of nutrients which causes calcium,protein and many losses, the hormones which are meant to flow through nerves ,it flow through blood and causes debilities. the i.b.s. happens through the miscordination in enteric and central nervous system, i think this problem is hereditary but i think lot can be done, i m really lukin forward to be a subject for i.b.s. reseach and want to contribute in the research. if there is someone who accepts my hypothesis and accepts my research proposal can contact me on my email id ***@****