I have been on tricyclen lo for over a year now. I never missed a pill and always take it as the same time every night. 2 weeks ago I skipped the placebo week and went straight to the next pack (so I didn't get my period). I didn't have any breakthrough bleeding or spotting until now (today). Also, I am sexually active and we don't use a condom. Last time we did it was 4-5 days ago. How possible it is that this spotting is due to a pregnancy?