It's more common that doctors and others will tell how far along you are based on your lmp(last menstrual period/last month period) which is calculated before conception took place this makes up your gestational age. However if you know when conceived you can follow your embryonic age which is based on the main implantation took place. So for like me I know when I conceived, I go by my embryonic age however if I wanted to know my gestational age I would just add two weeks- example right now my embryonic age is 30 weeks but my gestational age is 32 weeks. And for someone that knows their gestational age but they wanted to know when they likely conceived they could figure out their embryonic age by just subtracting two weeks from the gestational age and count back the weeks on a calendar. I don't know why the rule of thumb is to add or subtract two weeks it's how it's done for some reason. @jess_ji0715

what do you mean @loveless

Well if you follow your embryonic age then you are on track

my cycles were so irregular. my period was always so bad and so heavy...

Did you ovulate late? I thought I was 7 weeks and some change for my first appt and they saw nothing in the sack, freaked me out but turns out my cycles are way long and I ovulated late so I was two weeks behind. Hope that helps you!

yeah but that isn't that bad. I am 2 weeks behind.

Yes. When I was 7 weeks I had my ultrasound and baby measured to be about 6w5d

well my progesterone level was extremely low.

at 5 weeks, there wasn't a heartbeat for mine either. that's why they usually make you wait longer. it freaked me out, but I'm almost 36 weeks now :)

but there wasn't even a heart beat or a flicker

Yes. I thought I was 7 weeks about to be 8 and they said I measured to be about 6 weeks.