Help!

AF due 7/18 based on 30 day cycle. Reddish/light brown spotting 6/26, 6/27, 6/28. Never made it on my panties only when I wipe. I go see my doctor Wednesday. Any ideas on what may cause this? 
I have a 4 year old daughter and one I miscarried July 3 2014. 
Been TTC!