Niamh, you're being lovely and hard on yourself in the same breath, and gemma and Jo have already said the truest thing, so let me just make it really clear and add the bit that actually matters.
Direct answer first: brown spotting a few days before your test date is common, and on its own it does not reliably mean either that your period is coming or that implantation has happened. Both of those show up with spotting, and plenty of spotting is neither, it's the progesterone. The pessaries you're on are placed right by the cervix, which is easily irritated and can bleed a tiny bit, especially brown old blood, completely separately from your result. That is probably the single most common cause of exactly what you're describing.
A few things that DO carry information, so you know where the real lines are. The old idea that spotting means a failed cycle is simply not reliable, and so is its mirror image, that no spotting means it hasn't worked. Neither is true; the symptom is just noise this week. What matters instead is your official test on the date your clinic set, usually around 9 to 14 days after transfer depending on whether it was a day 3 or a day 5 embryo, taken on their timeline and not a day early, because testing early is its own special kind of torture and can genuinely mislead you. Our guide to the two-week wait explains why the early tests are so unreliable.
And the exception, the one thing I do want you to act on rather than ride out: if the spotting turns into heavier bright red bleeding with clots, or you get severe pain on one side, or you feel faint, that's a phone-the-clinic situation, not a wait-for-Saturday one. Also, please don't stop the progesterone off your own bat because of the spotting; keep taking it exactly as prescribed unless your clinic tells you otherwise. Our notes on the IVF medications cover why the progesterone matters through this stretch. You're nearly there. Come back and tell us how Saturday goes, whichever way.