Hello! Thank you for the query. Symptoms like diarrhea and constipation alternately, bloating, abdominal pain can appear due to large intestine diseases. It is more probable if you are around 50. And as home remedies like diet and probiotics have not given any relief, it is time to have some diagnostics and find (or rule out) disease causing it. Your symptoms can be caused by partial intestines obstruction due to inflammatory bowels diseases (like Crohns disease), colon polyps or even a cancer. And this diseases should be ruled out at first. To do that, colonoscopy seems most reasonable. Other possible reasons of constipation are medicines (antidepressants, Ca-blockers), thyroid diseases, hypercalcemia. It may happen that the reason of your symptoms wont be found and you will receive IBS diagnose. So in conclusion, it is definitely time to visit your doctor and have some tests. Colonoscopy, blood work, abdominal ultrasound, thyroid tests, calcium level should be checked. If all this tests will be negative, abdominal CT with oral contrast (enteroclysis) should be considered. Hope this will help. Regards.