How to be nice

I'm not great at talking to people, especially when I want them to like me but I need to take a pregnancy test before I can start birth control. But I can't take it until a certain number of days after unprotected sex. I need a way to tell my boyfriend, nicely, that we need to stop having unprotected sex so i can take the test. Every day that we do is another day we have to wait. Now I can just wait until I go back home later this month but if it turns out positive, I'd want him to be there. Any advice?