Is it safe to try a different laxative if milk of magnesia (magnesium hydroxide) isn't working?

Yes! The colon needs water & fiber to function normally. If you're not drinking > 64 ounces of fluids/day, or < 50 g of fiber a day, your colon can't work well. Fiber supplements (like benefiber 2 tbsp 1-2x/day) are great! if you have a change in your bowel habits, you need a colonoscopy. If everything looks okay, MiraLAX (polyethylene glycol) is one of the best laxatives, 2 tbsp 1-2x/day. But colonoscopy first !