5 month old not keeping down solids

My pediatrician had us start solids when he was 4 months old and for the first couple of weeks he did great but for the past three weeks he just pukes for hours after he eats. Went to the dr twice for how much he was puking and nothing seemed wrong so I took him off solids for a week and put him back on and he pukes all day again no matter what type of food I feed him... did anyone’s little one have trouble with solids and did you wait or just let him like and stink until he/she matured? Any advice welcome! Haha