6 month Solid food

Alexus

Hi so my Son just turned 6 months and he had his 6 month check up . At 4 months he was 14 pounds and at this check up he is 17 pounds he is exclusively breastfeed on demand when I’m not at work and when my husband watches him he takes 4.5 oz bottles of my milk. The doctor says he didn’t grow much and that we need to start solids 3 times a day along with his bottle but I don’t know where to start 😩 I wanted to start purées is this going to help him gain weight and somebody also said start putting cereal in his milk as well . I’m so lost I’m confused on how much he suppose expected to gain in 2 months because he had a growth spurt at 4 months . I’m so lost on where to start with solids and how many pounds did any of your babies were at 6 months that were breast feed.