Sounds to me like implantation bleeding! This is normally about when your period was due, and usually only last for a day or two. A bit exciting!
If it were me, given the terrible tester that I am I would probably go out and get a test ready to do on my first morning wee. This is usually where the hormones are at their strongest and you will more likely get a BFP if you are pregnant.
This pregnancy it took til about 3-4 days after AF was due before I got a half decent result on the stick.
Good luck - if thats what you are after