A Mom's milk supply, mirrors what your child is intaking.
Being he only nurses at morning and bedtime, your milk is producing enough for that.
A Mom, never produces huge amounts, as a child lessens in nursings.
And never as much, as when the child was a baby/infant.
Milk supply, does dwindle, as the child gets older.
Whole milk, organic and hormone free, is commonly available in grocery stores. I find it to be the same cost, as all the other milks. Or, from Costco, it is cheaper.
My daughter breastfed until she self-weaned at about 2.5 years old.
By then, sure, my milk supply dwindled, and mirrored her intake.
This is natural and normal.
My son, self-weaned at about 1 year old.
I still had lots of milk, but he hated nursing by then.
Whole milk, is recommended for children 1-2 years old. BECAUSE, the "milk fats" in it, is an essential nutrient, for brain-development. It is not just about the calcium.
You need to ask your Pediatrician, about how much WHOLE milk he needs per his age.
Eventually, you will have to buy, whole milk or other alternatives. So that as he gets older, he has a whole spectrum of nutritional intake.
Kids cost money.
Milk costs money.
But as I said, in my grocery stores here, organic/hormone free milk, costs the same as regular milk. But, if you go to Whole Foods, I have found the whole milk organic/hormone free, to be at least, $2-3 more than a regular grocery store for the SAME brand.