Help my son grow

Hi mummies,i have concerns regarding my 13 month old son.A lot of times we went to polyclinic for check up and each time they check his height and weight they say fhat he's not growing/keep dropping his weight/height.Genetic wise,i'm more on a shorter side where else my husband is abit taller. So maybe there is a link why he's shorter than average toddler?for his weight wise,we fed him everything and he eats everything well,bread,porridge,rice etc.HE EATS EVERYTHING!milk wise,from baby i am not able to provide breastmilk for him so instead we bought formula milk and has been feeding him the same brand up until he is one years old then we change to similac stage 3,will there be any help with similac? i don't understand why he is not growing up to the satisfaction of the doctors in polyclinic. Please help advice on how to make him grow taller and maybe put on abit of weight#pleasehelp