R.Y.
I never nursed exclusively (due to medical issues and low milk supply) but it occurs to me that 16 months is around the time separation anxiety peaks for a lot of toddlers. Maybe you can you introduce another way he can have cuddles and mommy time first then try cutting down the nursing. My son got very attached to his favorite blanky around 12-18 months (he still needs it to sleep at 2.5). The other posts sound similar to what I have heard about weaning.