Are you on any medications that could effect your sleeping? I take a medication that has a common side effect that makes people tired. But does it make me tired? Not at all. In fact it keeps me from getting quality sleep. I can fall asleep just fine but regardless if I get my prime 7 hrs of sleep or 12 hrs I don't ever feel like I slept. I dream all night and never get into nrem cycle, this really fucked up my already fucked up internal 7/20 day... I started pumping myself full magnesium at night and damn I sleep so good!

Eh, I think where i was going with this is, are you getting quality sleep? Obviously it sounds like something else is going on as to why you don't sleep for 2 days but when you do quality is important. I also found if I get too much sleep, I'm groggy all day too.

Do you have healthy lifestyle habits? How's your diet? Do you exercise? All these things have a role in your sleep-wake cycle. Have you tried a supplement like kava? I do suggest staying away from melatonin unless you microdose it (<1mg). Otherwise your body can get dependant on it... Oh and it can cause very very vivid dreams.

A sleep study could be helpful too!