new with BC needing to know how it works

Hi so I just recently got in BC I've finished my first 4 weeks and my boyfriend wants to try sex without a condom. He's a virgin so I know he doesn't have and sexually transmitted disease so I was thinking about it. Idk what to do. 
Do we use a condom?
Does he finish inside me?
Is the BC effective right now after 4 weeks? 
Anything helps just need to know a little more about what BC does to prevent babies before I do anything. Thank you.