Hi,
I have wildly irregular periods but by some miracle timed it right and am now nearly 12 weeks. The time between menstruation and ovulation can vary hugely in length but the time between ovulation and onset of menstruation, called the luteal phase, doesn't vary much. It's between 11-19 days. Basically once you've ovulated, unless the egg is fertilised, it can't hang around more than c 2 weeks before leaving the body as part of a period...
This is from Women's Health Wesbite, sorry if you know it already. Based on that, I would wait another week. I tested however 9 days after conception and had faintest of faint lines but then left it to 13 days after and was undeniably a BFP:
"Ovulation to menstruation
This phase is called the luteal or post-ovulatory phase. It is generally accepted that the time from ovulation to menstruation is always 12 to 16 days, whether your cycle is short, average or long. But while this phase does tend to be more constant than the phase before ovulation, recent research suggests it may range from 7 to 19 days.
After the egg has been released at ovulation, the empty follicle starts to produce progesterone as well as oestrogen. The progesterone causes the lining of the womb to secrete nourishing fluids. If the egg becomes fertilised, it plants itself into the womb lining and the follicle it came from continues to produce progesterone to ?feed? the fertilised egg.
If fertilisation does not occur, the follicle starts to break down and slowly stops producing hormones. When the follicle has broken down completely and is no longer releasing any hormones, the womb sheds its lining. This is your period. And so begins your next cycle."