Diaper Question

battybtags

Do you remember when LO switched from size 3 to size 4 diapers? DD is 20mos old and has been in size 3's forever. At her last docs appt she was just over 21lbs and I think the 3's go up to 28lbs. The 4's start at 22lbs I think. It just seems lately that when she poops it's always a blowout-either out the leg or up the back-although I will say she's been doing some HUGE poops lately (and maybe had a touch of diarrhea as well). I'm just wondering if I should try bumping her up or not. I know if they're too big, they blowout as well so I don't know what to do!