maybe he is teething, some teething babies are like that, as for my son he is 16 mths too and rejects porridge so what I did was gave him yogurt, pureed or mashed food eg: pumpkin, potatoes smoothie, oats but blended, apple and such... he eats
so I allow his teeth to pop out n will massage his gums to relax, once I feel he is well with no pain or discomfort then will continue with porridge or rice intake