Blood tinged Discharge?

Reba
Ok so I am sure this has probably happened to me before but since becoming sexually active I have started paying better attention to my body. 
I am on day 18 of my cycle and within the past two days have started noticing very very very faint blood tinged discharge on the occasional wipe. I do not believe it is implantation bleeding because all sexual contact was protected with a condom though obviously it is still possible. 
However, I think it I am past ovulation and don't think it is "O-spotting".  Any idea on what this could be? I am not super worried, just a little paranoid.