In 2.5 hours, one heavy-duty tampon was soaked through, so that I was aware of the distinct sensation of liquid exiting the vagina in squishy ways upon moving. I'm not sure how large a piece of uterine lining it was that squooshed out upon stumbling into the bathroom, but whatever it was, it squooshed out past said heavy-duty tampon. Said tampon, upon removal, featured a really cool large hunk of uterine lining, one at least two inches long.
Another heavy-duty tampon is in place, and for backup, a nice will-not-betray-stains washcloth folded over into the right shape and size.
(For the reassurance of those who may be worrying, I still haven't been around any unchaperoned sperm in recent years. This is all my own body's general menstrual weirdness.)