Letting him finish inside??

So I've been on the pill for over a year now, specifically Yaz for about 6 months. I've thought several times of letting my boyfriend ejec inside of me, but I'm terrified. I'm 19, and definitely don't want a child, haha. He's never pressured me in to it, as he's rarely brought it up. But out of curiosity, I want to let him "finish" inside of me. I'm usually pretty cool with my pill, but I've definitely missed it by a couple hours or so. How safe is it? Should I try it closer to my period? Any stories willing to share??