You have mentioned the things your son is not doing but not the things he does. Well most ‘milestones’ which an infant should achieve has a range like walking without support can happen anywhere between 11 to even 15 months of age. Does you baby hold furniture and stand it walk with support? Does he say ‘mama’ and ‘dada’? Does he wave ‘bye bye’? Does he hold objects in his hands and transfer them from one hand to another? If he is doing all of these things then you can relax and wait till he starts walking. A little encouragement and motivation would always help.