Ive been feeding Kai solids since he was a little over 4 months. I didn't feed him everyday. I was…

Ive been feeding Kai solids since he was a little over 4 months. I didn't feed him everyday. I was basically testing his allergies so i wouldnt have to do it when he turned 6 months. At first he was showing true interest. But now,maybe since he turned 5 months or a little after,he basically plays over it. What can i do to help him out? How long can he go with only milk?