[Always *]

I think when the other person mentioned birth control, they meant the pill. It's not a bad idea actually. Even if you don't have sex for years to come, it's totally legit to use the pill for other reasons (eg acne , cramps, etc). Before you do anything, I'd suggest learning more about birth control and other things related to sex because if I have to have one more conversation about how X or Y cannot lead to pregnancy, needless to say, I think there is something seriously wrong with sex education in schools, especially in the US, if people have to educate themselves at the end of the day.

If I were you, even if you don't talk about the penis issue, you can bring up your fears about sex hurting because of it. It might be a way to bring it up and see if he's ever worried about it too (eg "hey BF, I'm just worried that since you're so big it'll really hurt if we ever have sex"