Demonic two-year-olds...

OK, does anyone know: is there some age when two-year-olds become posessed or something? Josh will switch from moment to moment from being his normal lovable energetic fun sweet self to being some sort of monster who defies everything (even what he himself says/wants) and everyone and pitches the kicking screaming unresponsive-to-anything tantrums. I'm just curious...is this something I can do something about, other than pray for it to end, and attempt to deal with rationally, or just a phase that children go through that I just have to try to live through? Could it be a reaction to something or someone? Nothing has really changed in the past week, but he's gone from "normal" two behavior, to possessed psycho Josh...and like I said, it's anyone's guess from moment to moment what it will be. He's also been whinier, clingier, and grumpier than normal. He had a molar come in, but it's in...poked through a few days ago, and he's still doing this mess...
Today we spent almost 3 hours trying to go down for a nap. He was in bed pretty much that entire time, not like some days where he'll get up and play for 30 min. before becoming loud enough for me to hear him. The reason I was so insistant on a nap today was his behavior before I tried to put him down...the above mentioned whiney and tantrum stuff. This is not normal for him...until the past 3 days or so.
Please, if you have suggestions, or want to commiserate, or console or whatever, please leave a comment, even if you normally don't. I'm not really sure how much longer we can do this mess. This weekend wasn't SO bad, b/c AJ was home, but today I had to do it myself, already feeling tired/sick(ish)/blah. It didn't go well...obviously.

OK, that's me ranting and being emotional for now...I'm done...I should go eat, low blood sugar could have something to do with my state of mind.