Birth Control Effectivenss When Start Period Late

I started taking ortho tri cyclen lo birth control pills in September of this year (2010). I am a Sunday starter. I am currently on the fourth week (green "inactive" pills) of my third pack of pills. The fourth week of green "inactive" pills during my first pack I started my period exactly on time on a Sunday the first day of my green "inactive" pills. Now though, for the past two packs (pack 2 and the pack 3 I'm currently on) my period has started late on the Wednesday after the Sunday that I start the green "inactive" pills, which means I am late about 4 days and then my period does not last till the following Sunday when I start a new pack of pills (with the white "active" pills), meaning there are days during the "inactive" hormone free pill week when when I'm not on my period.

My question is

1)My most important question is If I am on the green "inactive" hormone-free pills week and I get my period very late (or if it ends early) on those days when I'm taking an inactive pill and I am NOT on my period, CAN I get pregnant during that time? Do I need to use a backup method of birth control during those times or am I still protected when on the "inactive" pills and I have no period?

2) Is that normal or correct if my period comes that late on birth control pills?
I was under the impression that when on birth control pills, I should always START my period on time.

3) What about if it starts late and ends early?