Toddler pooping so much

I know that kids usually go a lot but my son usually goes normally one or two times a day. But recently (the passed 2 or 3 days) every dirty diaper he has is pooped. Not diarrhea, just regular poop. I feel like it started when wic changed his whole milk to 1%. Not sure if that has much to do with it. I’ve changed like 6 pooped diapers today. This happened one other time and he got burned so badly I had to take him to the doctors because I was just really concerned. Is there anything I can do at home? I wouldn’t imagine this is very comfortable for him. Any advice would help, thanks.