At 4 Months Old I Tried To Give My Baby

at 4 months old I tried to give my baby solid food. started off with home made rice cereals. also tried cerelac. but he wasn't able to pass a stool for 12 days even when I already stopped feeding him solids. I reintroduced solid now at 6 months. I gave him puree of sweet potato but now again for 5 days he hasn't passed a stool. what food is good for digestion?