I also am anemic and it is not treatable through iron supplementation. I found out that my copper is deficient as well and that in order to absorb iron, one must be able to absorb copper. I still cannot absorb and have been diagnosed with pn all over. I was very fit and healthy. They don't know what happened.

It might be worth asking your doctor to check your copper and ceruloplasm. If you google those, you will see that copper deficiency can cause neurological problems. This happens from people who have had gastric bypass or celiac (due to malabsorption).
Heartburn drugs do interfere with absorption because they turn down stomach acid which is needed for breakdown and absorption of micronutrients. Hopefully it's something simple for you. Wishing you luck.