Hi closephine I'm in a similar boat to you so thought I'd add my tuppence worth for anyone else that's reading with a similar issue. I had a random bleed during the week (think it was 6dpo) however in my case I'm doubting it is a sign of pregnancy!
I've been ttc 16 months but got diagnosed in January with pcos, so my cycles can be a bit erratic and pre af sypmtoms vary month to month from nothing at all to symptoms which seem to mimic early pregnancy symptoms! But I have never ever had a mid cycle bleed before.
This cycle we haven't been ttc as DP had his SA test. I haven't been temping other than for a few days when I had ewcm and my temps did rise so FF confirmed ov. This was on the day of DP's SA appt and we hadn't dtd for 4 days by then.
When I had the spotting it was almost a rusty red colour when I wiped after a wee, then nothing at all afterwards or since. Like you, I usually don't get anything until 13dpo which is when I get brown cm then af comes late evening on 14dpo. The day before this happened I was feeling pretty rough so obviously my hormones have been playing up but I'm not sure why.
I'm not getting any symptoms right now other than the usual sore boobs, but I've been in a surprisingly good mood all weekend which isn't like me during tww at all!
I'm also due af on Friday, so it'll be interesting to see how the coming week goes and whether our bleeds amount to anything!