Birth control for teens

Victoria
I'm in a relationship with a guy for almost 1 year and a month, we're both 16. We've tried lots of thing in sex but what we haven't is he ejaculating on or in my vagina. To be honest, our first vaginal sex was weeks before the anniversary. We were always ready to do it but fear always stopped us until then. Another thing is that every time we have sex we fear, waiting for my period to come.
So I wanted to ask you, ladies, about birth control pills. I know they are a good and almost 100% sure method, but for what time period should they be taken? Like every day for a month or so? Are they suitable for teenagers? And is it a good idea to use them if I have very painful periods?
Thanks a lot! 💋