I went to take my Ortho Tri-Cyclen last night (Sunday) and saw that the last pill I'd taken was Friday's pill. I took both Saturday's and Sunday's pill at that time (pills 7 and 8 in the pack). I'm not actually sure WHEN I missed the pill--I don't always look too closely to see the printed day; I just take the next pill. So I don't know what night in the first 7 days of the pack I forgot. For how long should I use a backup method?