What Causes Spotting While On Implanon?

i amon the implanon birth control and i havent bleed ever sense i got it put it. so for about a year now. and i went pee earlier today and when i wiped gooey blood came out. but it didnt show in my urine at all. then i just went to the bathroom about an hour ago and it happened again but even heavier and im starting to get a tummy ache. what could this mean?