So confused...

So I am supposed to be at 13 or 14th day in my cycle.  I have an apt tomorrow to see the RE to see if I have any follies.  Last night around 1am I woke up to go to the bath room and when I wiped there was blood.  It was light pinkish-redish but this morning it was heavy and dark red.  I don't understand what is going on???  I am going to call the RE but they don't open for another hour.  Can anybody explain???