Pregnant on birth control?

The day before my placebo pill, I had a teeny bit of blood mixed with CM after a bowel movement. (TMI, sorry lol) I am on day 3 of my placebo pills and no period yet. I just have yellowish tinged CM today, and had slightly blood tinged CM yesterday. I took a test last Friday just in case and it was negative. Could I be pregnant? I also have been on the same pill, Apri, for 4 months.