Um, so are you taking the 3 weeks of active pills, one each day? That is what is most important. If I were you I would just take one pill each day because that is what you are supposed to do.
I'm kind of confused about what you're doing. Are you saying that you're worried that if you have sex on the day you take pill # 21 you can get pregnant because you take the inactive pill on the next day.
If that IS what you're worried about, you should not be worried. If you take every pill at the same time each day (on the correct day) you should not get pregnant.
Also, getting your period isn't really a valid pregnancy test. Most women still get their period the first month or so that they are pregnant. Some women get their period for many months into a pregnancy. The pill doesn't work on a day to day basis, it only works if you take it every day because it builds up your hormone levels.
Please read up on birth control or ask your doctor how it works.