My Baby Is 7 And Half Months Old.he Is On

My baby is 7 and half months old.he is on breasfeed till 5and half months,then because of chickenpox dr started dexolac and now he is partially breastfed and dexolac,he refuse to take any semi solid food except cerelac.i had recently shifted to new cityhe is just 7.5kgs,someone suggested me to start nan instead of dexolac because after nan theirs baby also gain weight and started crawling in just 6months and my baby is not able to get up by his own.