Why so sleepy?

So, after all the sleep I got this week, I had one day of running around.  The next day, I was exhausted!  I slept most of the day away - and I had taken the meds, so that makes it really weird.  These days I like to try to figure out the reasons for any unexpected sleepiness.  It helps to make it all make sense.

My best guess today is that I'm on an anti-depressant and I am not taking it as regularly as I should.  It is the type of medicine that makes you drowsy, but you get used to it.  I wonder if taking it will less regularity makes me more tired.  I suspect that may be the case.  So, every time I realize this is happening, I redouble my efforts to take it more regularly.  Only trouble is my constantly fluctuating schedule, and need to take it with food.  I guess that's a first world problem, so I am not complaining.  Just noticing.