Tread lightly...I am thin ice

The next person that asks me what my due date is just may get drop kicked. When they follow it up with "O WOW! You look like you could go any day now" I might just follow that boot to the head with a punch in THEIR baby maker.
I have to grit through my teeth when I actually give "my due date". Why? you ask...umkay.... let's talk about "my due date" for a minute. The original due date I was given is based solely on the first day of my last period...estimated...because even though we were trying to have a baby....by the time I got prego I had enough of keeping track of my cycle and just said to hell with it...we're just going to have fun, and if it's in the stars that we should have a baby...I'll be knocked up. ENOUGH with the pressure!
So when we go in for our first appointment, I make a guess-timation...that just happened to be...conveniently enough...my son's birthday....April 7. Hmmmm...a date that's significant to me anyway. Problem is... it was just a GUESS-TIMATION! The wheel of fortune says given that LDP our due date would be "somewhere around" January 12. I love the receptionist at my OB's office that acts like this is the deadline for taxes, and as certain as so. (Yes, I am very pregnant, and very grumpy about it.)
Baby has measured on the larger side since ultrasound 1. He's measured anywhere from 1-3 weeks larger than what that due date says he should. THE ENTIRE TIME! I've been given three different due dates now....January 12...as I've already stated, based on the possibility that the first day of my last menstrual cycle might have been April 7. January 9... based on the first ultra sound, Dec 28...based on my 20 week ultra sound, and January 3....based on our last 3D ultrasound revealing a 4.5 pound baby with measurements that lined up as such.
Whenever I go in for "check ups", Katie, our Dr's nurse, who is very sweet... and very chatty... talks to me about everything except for the measurements she is taking....blood pressure, fundal height...sometimes if she stops talking long enough to listen to the baby's heart beat she'll tell me what that is after she's done. So yesterday, because of all the due date madness, and the receptionist asking me, yet again, what my due date was before being called back to a room...I finally asked Katie where the hell I was measuring at. 38 weeks. Okay, so let me get this right...I've been given two weeks worth of due dates, the line backer growing in my ute is anywhere from 1-3 weeks bigger every time I have an ultra sound, and my fundus is measuring at 38 weeks....anyone else see a trend here?