“Are changing bowel patters a sign of IBS?”

Need to see gi and do blood tests. It could be ibs but if bowel movements are changing then should be checked out

Changing bowel patterns can be a sign of IBS. IBS is a diagnosis of exclusion. There are no tests to confirm IBS. Mostly, it is associated with anxiety or depression, and in periods of stress or depression, the symptoms exacerbate.

The first thing to be sure of is that you have screening imaging of the bowel, mostly the large bowel due to the incidence of colon cancer, so I presume you have had colonoscopy with a look also at the end of the small intestine. If that is all normal, then adding probiotics and fibre may fix everything in terms of regularizing bowel habits. As well if simple measures do not eliminate the problems and concerns, then doing a comprehensive digestive stool analysis looking at overgrowth of various organisms, evidence of small bowel bacterial overgrowth, parasites, lack of digestive enzymes, etc., and remember that at any age one can develop an inability to digest for example lactose, or certain fats, or certain proteins. Start with testing to be sure there is nothing life threatening, then push on from there for the most comprehensive testing if a simple approach is not completely successful. Keep in mind family history, if your dad had colon polyps or cancer, for example, or something else in his forties, be sure to cover those bases as well. And be clear if you have more stress, if you are drinking more alcohol like beer or wine, or too much fructose containing juices, etc.
Don't worry, but don't ignore the symptoms; you shouldn't have to put up with discomfort and want to get to the bottom of things.
Doc B