CD 19 and light bleed???

So I'm on CD 22 now, but on CD 19 I had a small bleed... literally only this on my underwear:

My AF isn't due until 26th of this month, so I still have just over a week to go. I haven't bled at all since, not even a spot. But I felt severely nauseous very early this morning, but I was never sick, I feel absolutely fine no temp at all. On the day I bled my temp was at its highest:

What could this be? Thanks!