Insomnia?

Recently, I have had problems getting to sleep.  I don't know if it is clinically insomnia however.  Typically, the problems I am having is getting to sleep.  Mostly, a few weeks ago, I was going to bed at a 'normal' time of around 10 or 11 and basically lying in bed thinking, "I should be doing X, Y, Z..."  Then, I would not actually get to sleep until 2 or 3 in the AM.  I finally decided that this wated 3-4 hours could be spent in productive activities.  So, against my better judgement, I decided to wait to go to bed until I felt I was absolutely about to pass out.  Now, my sleep schedule has shifted to going to sleep around 3 in the AM and getting up between 9 and 11.  (Note, that classes are held in my program from 2-6 in the evening.  So, this schedule works for when I need to be places).  I have started taking melatonin supplements to get to sleep when I need to, but often feel snowed the next half day after taking these.  I don't have any big revelations about this, I'm not sure quite what to make of it.  Is this normal?  Will I regret the decision to shift my schedule later?  I'm not sure yet.  Should I sacrifice sleep in order to to do more work.  I know that learning is not converted to memory until you sleep on it.  So, in some ways, cutting down on sleep is going to cut down on my learnin
g, right?  I won't know the answers till after the next exam... Based on the results I will be able to tell you how it worked.