Safety.

I'm very curious and have a few questions about the safety of inter course. I already know the likelihood of STDs and such. If your SO and yourself use the pull out method and they clear their tubes before each time having sex and you have sex on the days you're least fertile like during your period and a few days after, what is the likelihood of pregnancy? I know you can get pregnant at any time during your cycle. Also what are some opinions about the pill? I've been really considering getting on it.