What Causes Brown Vaginal Spotting?

I am currently 5 days late. For a day, I had some extremely light spotting when using the bathroom. A tint of brown on tissue and then it went away. I've only been pregnant once in the past 10 yrs which resulted in miscariage. I was on clomid last year but had to stop tx due to brain surgery. I don't want to waste time or hope to test if its just an early sign of menstration?