I've been on tri cyclen lo for 3 years and have never missed a pill. Recently I became ill on the first week of my pills and was having some vomiting. I took my pill on my regular time, 9am and vomited around 9:30am. I did not take another pill because I thought I did not have to and just continued taking my pills normally. Therefore I missed pill 2 of week one and did not replace it. 8 days later I noticed I was starting to have some brown/light brown discharge and has continued for now for a little over a week. I am very considered about being pregnant right now, since I had protected sex (but i think some of the semen slipped out)6 days after I missed my pill.