Private scan- told different due date

[Tay2019]

Background info-
Had my LMP 10th January, conceived 18th January and according to Flo app ovulated 23rd January. Apparently I am 8 weeks1 day, went for a scan today, and they could hardly see the baby, they only measured 3mm and there was a tiny pulse showing a heart beat. She believes I'm 5-6 weeks not the 8 but I always thought it went off LMP now I'm not sure how far along I am and I'm just worried, we could see the sac and a line but not an image of a baby like in my first pregnancy at 8 weeks, I couldn't even tell there was anything really there.

Has this happened to you? Do the dates show I'm 5-6weeks or the ones I thought initially and what do I do about my knowing when I'm actually due and updating this on my files with the midwife.

When did you first get a positive pregnancy test?

It's impossible to conceive before ovulation, so the date you conceived is actually your ovulation date. Do you mean you had sex on the 18th, and then no sex again until after the 24th? If so, I think it's unlikely you ovulated on the 23rd, because that would mean the sperm had to survive inside you for six days, and they are known not to survive for more than five days.

If I've understood the situation correctly, your Flo app is talking rubbish! Unless you track BBT and had a clear and sustained rise on the 24th/25th? If not, Flo is guessing. Did you have sex anytime in the three weeks or so after the 23rd? If so, perhaps you ovulated late and conceived much later than you thought.

If I've misunderstood though, and you had sex closer to the 23rd, and you're certain (the only way to be sure is BBT) that you ovulated on the 23rd, then I'm afraid it doesn't look good. Private scans are notoriously unreliable, but that is a huge difference in size and seems an unlikely mistake for them to make.

Sorry to add to it I did a test on the 9th Feb and it was positive. I did one on the 10th it was positive. Only did it on the 18th as Jan. I'm doubting the reliability of the app I know itcan vary too. I'm so confused now.

So are you saying the last time you had sex was the 18th Jan? If so I think that this pregnancy is not looking good. I'm sorry 😔

They always date pregnancies from LMP to start. But this is because people often do not know when they ovulated. Measuring 5-6 weeks when you are meant to be 8 weeks isn’t a good sign in my opinion if you know you definitely ovulated when you think you did. However because you only use an app to predict it you can’t know for definite.

IF you ONLY did have sex on 18th January then you can’t be under 8 weeks and personally I would prepare for the possibility of a miscarriage. But you need to have another scan in a week or two to confirm this. Obviously if you have had sex after 18th it’s possible you just ovulated much later then you thought and are much further behind. It’s also possible that if it was a private scan that they just aren’t that well trained and they are wrong. I would try and get a scan at an EPU personally to check.

How long is your cycle normally?