Hi, I went through the same thing when my son turned one year old. When we switched from formula to whole milk he got soooooo constipated. We took him to a pediatric gastro who did tests and said he was fine. The dr. told us to use kondrimuel or mineral oil in his milk and it did help a bit. On our own without advise from a doctor, we switched over to soy milk and he was fine....... after that he switched to lactaid milk and he's still fine. We monitor his dairy and try not to let him eat too much cheese. IF he is eating alot of chesse or milk, I put about 2 tbspns of mineral oil in his chocolate milk and it does wonders. You should take this serious. IF a kids associates "movements" with pain, they will hold it back and then it's a serious problem. Good luck and feel free to email me.