Hi, should i stick to giving my 13 month old boy formula or switch to cow's milk already? understand we should be giving our LOs full cream milk now but formula's skimmed milk right?

I feed formula for my boy - and he is 3 years now. I know I know - there is all the talk about formula being artificially made, not natural etc. but for me - I feel that's the best and it's my kid anyway =) so it's your choice!