I thought your AB's could be the cause also. With both my boys I had the "clean out" happen the day before & day of labour.
It was the full on runs either, just alot softer then normal & more frequent. But it wasn't running to the toilet before I mess my self KWIM.
Mention tonight for sure & make sure you keep your fluids up too. Maybe some probiotics to settle down the flora in your gut. The AB's would have messed with that.