In the past month I've met two former vegans who were having energy problems and were diagnosed with anemia (both female). They were always fatigued, even their mental state was sluggish, and they rarely went out in the evening because they were too tired. Their doctors advised them to start eating meat, which they did, and now they feel so much better they're not going to consider veganism again. Anemia is a real problem and not just for vegans, but I think it's especially harmful to the reputation and validation of the vegan diet because it is preventable.
Have you been to a doctor for a blood test, specifically to check for iron and B12 levels? In the meantime, try a liquid B12 supplement under the tongue, and make sure you eat lots of iron-rich food with vitamin C rich food which aids iron absorption, and see if anything changes (often, the problem isn't how much iron we're getting, but our ability to absorb it).
Also, and coincidentally, I'm hosting a show this Tuesday on veganism, women and anemia because I want desperately to prevent another woman from telling me how much better she feels after eating meat! So perhaps you could pm me your symptoms and any questions you may have. I'll be interviewing Vesanto Melina, co-author of Becoming Vegan, and we'll have a general question and answer session as well, so I'll bring up your question. (You can listen live at www.ciut.fm
at 11 a.m. EST, or download the podcast or mp3 from our main site, http://www.animalvoices.ca