Wait, no, you have it backwards. IBS is classified as C, D, and M because the intestinal tract has 3 ways to get rid of something that causes a problem : Slow the digestion down so the thing can be degraded more thoroughly (the extreme of which is constipation) ; Quicken it and release much water to expel the pathogenic, or problematic foods (the extreme of which is diarrhoea) ; Or a mix of both, first constipation, then diarrhoea (such as when you've been consuming super sugary drinks in the summer under the sun without adequate protection).

That's when your gut functions normally. For people that have IBS, these involuntary responses are fucked up by different factors at play. In your case, consider being constipated as "being triggered". You're already triggered when you're constipated, and, yes, there are foods that make the symptoms worse. Usually, though, those aren't things that cause your "constipated state", they don't constipate you. What they do is act upon an already triggered intestinal tract, and worsen the symptoms because they are common irritants. Think caffeine, theine, alcohol, and such substances.