7 months old boy hyperactive since birth

Hello, our child is hyper active since birth and till now we managed to feed breast milk as he wanted by making him sleepy. Since we started giving solids after 6 months, he started eating well with a lot of our efforts to keep him engaged. Since he doesn't empty the breast, he doesn't take enough milk from mother. We had started formula milk by giving with spoon he had gained enough weight till last month, now he prefer activities over food he is now only7.3 kg. He used to have 6 kg when he was 5 months old and 2.7kg at birth time. Nowadays he holds milk in mouth and doesn't swallow, though we changed the different flavours as doctors said, still he doesn't drink. He will have solids of 1 small bowl with 1 hr of our efforts. Could anyone suggest how can we encourage our baby to have formula milk and food to gain weight by making him calm and focused??