part of me wants 12 weeks because I seem too big for 8, and I'm excited to be further along.
another part of me wants 8 weeks because i'm sooo NOT ready yet!!!!
I cave a lot of loose ends to tie up before this kid comes.
I'd go with the 12 weeks as well. You should be having an ultrasound fairly soon anyway, so the dr will be able to date your pregnancy a lot better then.
id go with the last period like the dr.'s office. it may not be 100% accurate but it makes the most sense. so id say your 12 weeks!