Hi Justine-
Well as far as the birth control pills go...when I was 20 I was taking my pills everyday at the same time and got pregnant still. I now have a beautiful 4 yr old and there were no complications from taking the pill and getting pregnant.
A friend of mine just took the plan-B pill about a month and a half ago and just got her period for the first time since then. If it were me I would take a pregnancy test again and then start taking your birth control pill.
Also you asked about getting pregnant during certain times of the month. The usual time is about half way through your cycle, although everyone is very different and women who have wacky cycles can ovulate at different times of the month. Don't rely on when you are supposed to ovulate. If you DON'T want to get preggo than you need to get on birth control right away. Also you will need to use protection/back up method for the first 7-10 days after starting the pill and make sure to take it at the same time every day.