Second Wedding Freak Out

(Originally drafted on Thursday, 5/8)
I had my second wedding freak-out this morning. If you don't already know this about me some might say that i obsess about certain things. One being my ability to adequately plan ahead and be prepared... A little OCD about a few things. So, for my wedding invitations I was hardcore about making sure I had the correct postage. Dad worked at the post office and warned me that he had to give some bad news to some brides b/c they didn't have the right postage on their invitations. I knew that b/c I was over 1 oz and the envelope was not a standard size (it was square) that I would have to pay more for my postage.
In the days leading up to mailing the inviations I went to the post office THREE different times and had the guy weigh it every time and factor in the cost for the irregular envelope -and everytime i went he told me that it was going to be 75 cents. So I bought a bunch of 75 cent stamps.
So.... Significant Other and I stuffed, sealed, and stamped all of the invitations and I took them to work with me this morning. I stopped in at the Union Station post office since i didn't want to carry them across the Hill to my office - and after waiting in line for about 5 minutes - and with a long line behind me - I asked the lady at the counter to confirm that I had proper postage on the envelope. She said....
No!
She said that I was 22 cents short. I asked her if she was serious - yes she said. I told her I had 67 of these envelopes and that I couldn't deal with this right now - and I left.
On the verge of tears and quietly trying to calm myself down so that I totally don't start screaming I walked across the Hill to my building. I went to the post office in the basement of my building and handed the guy the envelope. I asked him if I had correct postage. He said 75 cents "should" get them to their location. Huh? I was soooo drained and I didn't want to deal with it any more - so I said fine - and handed him all of my invitations. Hoping upon hope that the lady at the Union Station post office was just mistaken.
UPDATE: 5/12: so.... apparently i was 22 cents short - FOR SOME OF THE INVITES but not for all. What could be the cause of this? I asked my dad who said that i was probably right on the verge of going up to the next ounce (22 cent increments) and that some of the scales at the destination post offices might be "off" and therefore SOME of my invites might be 22 cents short.
Of course it is totally random and I have no way of knowing whose invitation this will impact. This lovely situation occured with my fiancee's parents - they got a notice from the post office that there is an envelope waiting for them "postage due" and that if they want to get it they need to go to the post office and PAY 22 cents to get the freaking invitation. SERIOUSLY! This also happened with my aunts and uncles in Wisconsin - but not for folks in Baltimore or DC.
VERY UPSETTING but there is nothing I can do..... I will just need to call people in a few weeks and ask if they are going to come or not. I doubt I would go to the postoffice to pick up a postage due envelope.
I suck.