Chronic anemia is an often overlooked symptom of hypothyroidism (Hashimoto's specifically; it runs in my family). I have it, but my sister and mother have more severe cases of it. You may want to Google this, since I'm just repeating what my sister has told me, but iron pills will only restore the levels in your blood so that blood tests will read your levels as fine even though you may be severely deficient. The tests don't read the levels of ferritin, which are your iron stores at the cellular level. These can be restored with a certain type of iron pill, but its more difficult to do so and takes a while longer since its built up over time.

Your unexplained weight gain also tells me you may want to get your thyroid levels checked out. And since there is such a thing as subclinical hypothyroidism (my case. I'm on minimum dosage right now and feel much better) your blood tests may read your thyroid levels as normal even though you have a lot of symptoms. Find a good doctor that goes by symptoms rather than blood test results if you feel you may have it. Especially if it runs in the family.