Very light bleeding during period

I was 3 weeks late when I started my period. Today is day 5, and all I have had is very very light bleeding. The blood is brown. Its so light that I dont need a pad. Just when I go to the bathroom and wipe, there is a tiny bit on the TP. Any ideas as to what this is? Or what has caused it?  I have had very regular periods most of my life, and since Ive had my daughter which was almost 2 years ago. I know that I could be pregnant since I was late in the first place, but I dont have any pregnancy symptoms at all. no breast tenderness, no sickness, etc. any comments or answers would be great. thanks!