Ear Pain following tonsillectomy is a very well known complaint and it will pass off very soon. Reassure the child and coax him into inducing lot of swallowing movements like by drinking cold things or ice cream or simply asking him to chew a gum. Constant swallowing will make the pain go faster. Constipation generally doesn't last that long but since he has had no intake of fluids, so don't expect anything great from him. Relax and do see your doctor after 7 days.