Well, I'll take a quick stab at it.
The way I see it, you have simply been pushing yourself too hard for too long. The extra course at school this semester may have been just what it took to push you over the top.
You are getting the sleep that you would normally get but you aren't getting the rest and relaxation.
Let's see how close I am with this one. You go from work to school, grab something to eat quickly between the two. After class you go home and do more work before you go to bed. Or if it's not work then you do some schoolwork, or sometimes both.
When you do hit the pillow you are thinking about what you have done during the day and what you will be doing tomorrow. I'm betting that you are thinking about those things while you are asleep as well, as stupid as that may sound.
Your weekends are filled with more classwork and also work that you've brought home from the job, right?
I think you need some good, quality "osuche time" where you relax and enjoy life without thinking or worrying about school and work. And I think you need it on a more regular basis, not just every once in awhile. You've been on one hell of a pace for quite some time now osuche. Probably too simple of a solution but I really think that your body just isn't getting the chance to recover from your stressful job and classes and it's just sort of deciding to do it whenever it wants to.
Just my thoughts on it.
(((((((Osuche)))))))
Time for me to try again to get the sleep that I'm needing.
