implantation or period?

am on birth control. I missed my pill last week but took it asap the next morning. I haven't bled all today but today at the gym, I was running and all of a sudden I feel wet. I go to the bathroom and its almost like a maroon color blood. not too much and a consistency almost like snot but a lot smoother... it just came out with no indication... what is this?? I am on my last week of combination pills also so period not due for about 5 days.. no other symptoms