For those with 28 day cycles and ovulation on day 14, implantation is, on average, most likely to successfully occur on day 8,9 or 10.
However, the normal range for a successful pregnancy is 6-12. So, while the majority of women will implant on 8 9 or 10, some will implantation later and some earlier.
When you get your bfp doesn't just depend on implantation day, it also depends on:
- the sensitivity of the test you're using
- your starting beta hcg (between 0.1 and 5)
- how fast your hcg doubles (36-72 hours)
If you have a base hcg of 5, use a frer and hcg doubles every 48 hours, you can get a bfp the day after implantation, so a 8 or 9dpo bfp is a 7 or 8dpo implant.
It's worth noting that most women will not get a bfp before 10dpo, while it may seem like most women on mumsnet do, it is not an indicator for the greater population.
I'm certain I implanted late night 5dpo (could have been 6 if I ovulated day of peak not day after) as I felt it, but didn't get a line until 13dpo pm (may have showed fmu 12dpo, but i didnt test), likely because I have lower base hcg of around 1.
So, even if you do implant earlier there's no guarantee you'll get an early bfp.
The blastocyst kinda floats around for a bit before implanting, just chillin' in the womb.