Hi I've been on MTX for over 2 years now and yes, it can cause extreme fatigue at times. I'm currently on a very big dose of the medication I have LGL Leukemia in addition to my RA/Lupus. The leukemia can be treated with a form of MTX injections too. However, the dose is much higher than you would normally would take to treat your Lupus.
You didn't mention if your Rheumy has you on Folic Acid to help counter the side effects of the MTX. Most folks who are on MTX take Folic Acid to help with the side effects. I take 1mg of Folic Acid daily prescribed by my Rheumy. It's just a thought, but maybe you could ask your Rheumy about prescribing it for you. You could try taking it and see if it works for you. Are you having any other bad side effects from your MTX?
I hope that you begin to start to feel better really soon. I hope that the MTX will also begin doing what it's supposed to do for you. I know this is hard to deal with all the fatigue, symptoms and pain. Just hang on tight and hopefully you'll begin to feel a lot better before you even realize it.
If you have any others questions please ask away. Someone on here should be able to answer your questions.
DX- RA, Lupus, Fibro, LGL Leukemia, Obstructive & Central Sleep Apnea, Pulmonary Hypertension, Bells Palsy, Gastroparsis, Blood Clots, Glaucoma, Chronic Pericarditis & Pleurisy, Severe Anemia. Way to many medications to list.