So AF showed up 2/9, then 3/5. which makes 25 day cycle right? Anyways, I found out I was pregnant on 4/6. My due date should be when? I though 12/10, early u/s says 12/15... I'm clueless at figuring these things out. Don't see the dr til 4/30.. also can u guess the date of conception that way too?
U/S is by far the most accurate way of calculating your due date.
Because you can ovulate at any time during your cycle and because you have no idea when conception takes place EDD based on your LMP and even ovulation dates are never going to be as accurate as an u/s. I'm sure your OB or M/W will explain this at your next appointment :)
Your prior cycle really has no impact as every cycle is different.
If your last cycle started on 3/5 then (assuming average O on the 14th day) your EDD would be 12/10. But it could easily be 12/15 if you have a 33 day cycle or O'd on the 19th day.
Also, depending on your US, it could be off a few days, too.