figuring out a due date

So I have been looking for those due date calculators online and I am getting conflicting info from them. I think doing IVF makes a difference in how it is calculated but I am not sure how it affects the date. A couple have given me July 12, 2012 so I am going with that. I also got July 15 from one of them. Of course if I have twins, it will be more like mid-June. But we will cross that bridge when we get there.

Technically, I am 4 weeks 5 days and into my second month. It sounds so far along considering I was suffering the 2 week wait just a week ago. Of course I have a long way to go.