Weaning himself?

My son is 12 1/2 months. My plan was to BREAST feed him until 18 months, then give him my milk out of a cup til 2-3 years old. The past few days to a week, he has been drinking less from me (he eats table food well) and seems to want to use me more as a pacifier and BITES a lot. Could he be weaning himself? He still nurses through the night A LOT. He doesn't bite at night either. But daytime feedings are rare, short and becoming painful lol!

Let me be clear- I am NOT emotionally prepared OR ready for this.

Also, for the pumping mamas, how do you keep your supply up with no baby nursing? I'll be strictly pumping for at least a year if he is weaning...

Thanks in advance!