You're busy because you have to take care of your friend's ice ogres (いそが) this weekend. You don't know why you agreed to this, you were busy enough, but now you'll never get anything done running around taking care of these little ice ogres.
I'm so busy that my head is spinning.
Don't expect a quick email response from Koichi, as he is really busy.
Today was hectic. Just today, we learned 1000 new Japanese words.