From day 1 here, too.
Let's just say the nurses on the floor had to have a meeting regarding my nipple - difficult child had, um, sucked too hard. doctor said he never saw a baby with that tight of a grip. Colic, ear infections, etc. Terrible twos meant nothing to me because nothing really changed - she was always a tough kid.
Something did change though around 7 - I am not sure if I suddenly had less patience or if she just started being more defiant. Sometimes I wonder if I expected more of her, just things that would have been expected of a 7 year old and she was not capable.