Just figure in your 2ww, and go from there. I used my ovulation date, which when I plugged it in, the LMP given was, as expected, was days later than what it actually was!
I would say if you did IVF, then you're at least four to five weeks along. I know, it's darned confusing, and if you go to books or other websites, it just seems to muddy the waters. Here's how the IVFConnections website calculates your weeks:
How many weeks pregnant am I?
The start of an unassisted pregnancy is usually measured from the first day of your last menstrual period. When calculating, how many weeks pregnant you are after an IVF cycle, start counting from 2 weeks prior to your retrieval. For example if you had a positive pregnancy test on November 30th and your retrieval happened on November 14, you would now be just over 4 weeks pregnant. **Please note that some clinics calculate the estimated due date differently. To be more precise, always have your clinic calculate the due date for you.
I found a couple of sites on estimated due dates, but I finally found one that also calculated how many weeks along you should be, and it's showing 5w4d.
Hope that this helps! Take care, and have a great weekend!