I would recommend trying Gas-X first and if that doesn't work, I would try Metamucil. I have never seen side effects from Gas-X. Metamucil can sometimes make you feel bloated but that is rare. Metamucil is not a laxative and should not cause you to go to the bathroom more often. It binds stool together and allows for more formed, soft stools.
You can develop lactose intolerance at any age and out of complete blue. The best way to diagnose lactose intolerance is based on your symptoms which include gas, abdominal bloating, and/or diarrhea. There is a breath test which can be done to diagnose it but it would be much simpler if you eliminated dairy for 5-7 days to see if gas improves. You can substitute regular milk with Lactose free milk, avoid ice cream, sour cream, and cheeses. You would just experiment with this for a week or so to see if your gas improves.
If Gas-X, Metamucil, or eliminating dairy does not work, I would suggest you speak to a gastroenterologist for a possibility of having Irritable Bowel Syndrome (IBS). IBS can cause similar symptoms but it is a diagnosis of exclusion (which means that when other conditions, such as lactose intolerance, are ruled out, IBS can be diagnosed). There are multiple treatment options for IBS if that happens to be the case.
Hope this information helps more. Please feel free to ask any other questions you might have.
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