Who are you, and what have you done with my sweet boy?

My sweet, innocent little (almost) 19mo old has had a challenging week, and so has Mom & Dad. Is it possible that the terrible two's have arrived - 5 months early??!! Is there a specific diagnostic test for this "terrible two" stage? Here are the symptoms:

• He tries hard to express himself in words, but still can't (at least not in a language that we can decipher). He gets extremely frustrated with us when we don't understand him and meet his every want & need as demanded immediately.
• He regularly throws toys or food or whatever is in his hand when he does not get what he wants. Then he usually cries, because he realizes that he wants to play with or eat the item that he threw...
  
• His favorite word is "NO" and he uses this word in repetitive form, gradually increasing in volume as if pleading. "no, No, NO, NO, NO!!!"
  
• He regularly practices the "Open Mouth Trust Fall" (as we have named it) - he falls backwards onto the ground flailing arms and legs in protest. He takes it for granted that one of us break his fall.
  
• Sometimes, he gets so frustrated that he hits himself in the head with toys or pounds his head on the wall as if to punish us by making us watch him hurt himself.
  

Thankfully, Keaton cheers up just as fast as he gets angry, he does not hold grudges, and is easily distracted from his tantrums. It's amazing to me how pre-programmed we are as parents to love unconditionally. Who else in the world would we allow to treat us like this? No matter what forms of suffering I am forced to endure the during the day, I still count the minutes until I can get him out of his crib in the morning or pick him up at the church nursery. We'll see if I feel the same way about Mr. "Terrible Two" after a week at Grandma's house... yikes.