@luthienrising Thanks for the reply ^^
I redownloaded the mod and tested it without other mods and it seemed to work fine (at least they weren't showering or cooking every 2 seconds) though I don't know if this mod is actually still working because I don't have any infants in my families right now.
I thought it must be conflicting with one of my mods but it worked fine with every mod I have, even when I put all my mods back. I aged one of my Sims down to a child because she aged up to teen after I removed the mod and once she was a child, my Sims started being obsessed with showering again.
According to the Mod The Sims page, it looks like Easier Infant Care alters the sleeping behaviour of child Sims so I guess it conflicts with a mod that also changes the sleeping behaviour of Sims. (Probably the SleepIn mod by LMS?) I'll try it out once I'm home.