I've had all the further testing run under the ANA, and all comes up negative, so my docs are telling me the elevated ANA is "false positive." I understand this can happen, a certain number of people have it elevated, yada yada. BUT, in light of my symptoms,and the fact that it was 1:160 a few months ago and 1:320 last week, I'm concerned.

It is not uncommon to have elevated ANA after a pregnancy.
This is the body's reaction to the fetus. Some women get this and it typically resolves with time after delivery. (even my own doctor had this situation).

The ANA can fluctuate in people between elevations and then followed by periods of normal. Doctors know this and typically retest after several months pass.

So far your testing results suggest a macrocytic anemia. I'd follow that path for now, to treat that.

Pregnancy and long term breastfeeding can be stressful on some women, as the nutrients the baby needs are taken from the mother. Human milk, is high in fats, cholesterol and glutamine for the baby's early development of the nervous system and GI tract. There are some prenatal vitamins out there especially for pregnant and breast feeding women.
This is one:
http://www.amazon.com/Expecta-Lipil-.../dp/B001F0RA34

DHA is a long chain fatty acid used to build the cell walls of neurons in the brain and spinal cord.

Some RX prenatals also have DHA in them, but not all.