Confusing due date😔

I • Sat, Nov 21

So I thought I was 10weeks pregnant, according to my lmp. The nurse gave me June 23, 2016 as my due date. I go into the ER on Thursday due to cramps, but no bleeding. And US showed that I'm now 6weeks pregnant. Now my due date is said to be July 13, 2016. Is that normal? That's a whole months difference