Clear Blue Easy Fertility monitor.?

I have been using this and since day 12 it has given me the second bar. It is now day 17 it is still only on the second bar. This is my first month. I don't have the paper work that came with it. Is this normal? Can someone be "fertile" for more then 6 days. I am with my other cycles like 30 to 32 day cycle. This is only my second month since going off BC. This will be my 4 child. We are using it this time because we have 3 wonderful beautiful girls and have been told that if we BD on the exact day I ovulate we have a higher chance to have a boy. Although a boy was be so great as long as we have another healthy baby that is all we want.