Hey, just wanted to clear a bit up here, since I'm no doc.. and I went to the doc and found out more. I do have low B12 and yet my iron levels are fine. So it is possible, and low B12 can cause fatigue, depression, sores around the mouth, tingly hands/feet, and headaches.
Either way, both iron and B12 levels should be checked in a blood test. Not sure if you have gone yet, but next time you do ask your doc about it.