What Causes Fatigue And Excessive Sleepiness?

I have been experiencing an abnormal amount of weakness and weariness for the past several month...to the point all I want to do is lay around ad sleep. I have considered all possibilities as to what could be causing this and only last night was listening to a documentary that mentioned that methotrexate was a form or cemo-therapy that made me think I ought to investigate the possibility that this medication may be causing this weakness. I also now remember that for a few months I have not been taking the folic acid that I am suppost to take WITH the methotrexiate...my Humana quite filling it and I just kept forgetting to followup on getting it somewhere else or apposing them about it. What do you think...could this be because I have not been taking the folic acid? SO Sorry -- just realized this costs money and can easily contact my doctor tomorrow with this question...sorry to take up your time.