How much spotting is normal? (Also, when in your cycle is it normal?)

When (and how much) spotting is normal? I’ve noticed some light brown/tan spotting recently (it’s very light; light enough that it doesn’t get on my panties - usually only a small dot when I wipe). When the spotting has happened...

-It first started 3 days before my last period (10 DPO in a 13 day luteal phase). I don’t recall ever having it more than a day before my period in the past.

-I then had a 5 day full flow period as I always do. However, on CD6 & 7, I had some light brown mucus-y spotting when I wiped. Usually my period stops completely after CD5.

-Now, I’m on CD10 and have noticed the tiniest light brown dot on the TP every time I’ve wiped today. I did have sex last night and was unusually dry, so I’m not sure if that’s why. It’s the first time I’ve ever had mid cycle spotting, so I’m a little worried.

I’ve been TTC for a while (over 6 months) with no luck, so the spotting has me alarmed. I have a very regular cycle and ovulate at the same time each month. My estradiol, AMH and FSH levels have been tested, and they are normal.