SOOOO Pissed...Dr Bill

I seriously just a doctor bill in the mail...from 12/7/11!!!  This was a time when I was taken to L&D after one of my many growth ultrasounds/nst where the stupid tech took forever, leaving me on my back for too long, causing Ian's heart rate to drop.  I'm so mad right now I can't hardly even type for crying!  I paid everything in full when I got my income tax money this year.  This should've all been done and over with.  So, I called the billing office and they said that they never sent me a bill on this.  So, I asked why in the HE!! am I just now getting one almost a year and a half later?  They had no reason, other than the fact that it "probably just got over looked, and they're going through accounts to clear up unpaid bills."  WTF?  After I had Ian they waited a whopping 2 months before I was sent to collections, for the bills from having him...but they're just "now" going to send me a bill for something prior to that time?  I got a bill from this.  I remember getting it because I remember the total and I remember being pissed off then that it was going to be included in on what I was paying towards my deductible, ahead of time, for delivery because it was going to be in a prior year.  I had to go twice...so I very specifically remember this.  My insurance company is closed for the day so I can't ask if they have a right to even bill me for this.  I'M SO PISSED!  Every time I think I might get ahead something like this comes up and I'm taking 100 steps back.  And times like this make me fuming mad at exSO because once again I'm stuck with a bill related to our son...I paid every penny out of my own pocket for having him, he gave me nothing...all copays, all deductibles, EVERYTHING!  EVERYTHING!  I'm sorry, I needed somewhere to get this out...sorry it had to be to you all!