Maybe stupid questions, but I’d honestly like to know

These may be some stupid questions, but I’ve really never been taught thorough sex ed, so maybe you ladies can help me out with a few things?

About how long is the window of time between sex and realizing you’re pregnant? Does it vary?

Say I had sex about a week before I was supposed to get my period. If I got pregnant from that sex, would I still get my period in a week, and miss the next one? Or would it “take” right away and I would miss the period the very next period?

I’m still a virgin, but have talked with my boyfriend about starting to have sex (we’re both 18). I am paranoid of getting pregnant, but cannot take a birth control pill in my situation. If he wears a condom, would it make a difference in chance of pregnancy whether he ejaculates inside of me or pulls out beforehand? Not exactly familiar with the norms here. 😬

My mother’s side of the family is apparently extremely fertile. Any tips on whether or not that should change my habits in avoiding pregnancy?

Sorry if these have obvious answers and I just don’t know them, but thank you if you can help me out! ❤️