bleeding between periods

Jas • 20. TTC baby #1
Every month I have spotting in between my periods and I don't know why. It isn't heavy & its usually brown. Yesterday I thought I was starting my period a week early but it just seems to be brown and pink spotting with some red drops. I don't know what to think! My Dr has brushed me off, saying its nothing to worry about. Does anyone have similar stories?