You'd have to be what they class as at least 3 or 4 weeks pregnant for a HPT to show positive. That of course would not explain all those weird symptoms you had earlier though.

I'm just thinking that seeing it didn't show in a HPT or a BT back then you can't have been pregnant at that time therefore it's likely you just O'd later & got pregnant later in the cycle than you expected to. A dating scan will confirm this (or prove that theory completely wrong if you are further along).

Dating scans are pretty accurate, usually you have one if you've had a long cycle or a suspected pregnancy that hasn't shown up in earlier tests or if you are having an NT scan (to make sure you get it done right on 12 weeks).

I will be very interested to see how it all turns out. I had 3 pregnancies last year & therefore was in three different belly buddy groups at different times. In that time I saw several women that were at completely different stages of pregnancy to what they thought they were once they had an early scan done. Some were maybe a week out one way or the other but I've also seen people up to 3 weeks out from the date they thought they were & they had to switch buddy groups. I was very envious of the lady who went from 10 weeks to 13 weeks overnight, not so the one who went from 8 weeks to 6 weeks.

Best of luck with the doctor's visit. I'm sure the BT will come back + this time.