Pull out or not?

Okay. This is my first time posting in here. But here's the situation. My boyfriend and I have been living together for 6 months. Which is also how long we've been together. I started living with him before we actually started dating. And we see each other every day, spend every day together, and we don't fight about anything! We are both so ridiculously happy. Yeah now and again we get a little irritated with each other but we always talk it through. And as cliche as it sounds, we plan on being together forever. We've found "the one" we talk about getting married and having a family almost daily. I'm so happy. So here's the thing. We're both 20. And we have sex multiple times a week (not EVERY day but pretty close) and the last couple times we've had sex, he's told me that he wants to cum in me...and I've been thinking that I want him to. During sex he will even tell me that he's about to cum and he will say "do you want me to pull out?" And every time so far I've said "yeah it's probably a good idea that you do". It's not that we are trying to have kids. We do want them in the future but if he came in me and I did get pregnant, we would obviously take responsibility. But I have friends whose boyfriends have cum in them more than once and they don't want kids but haven't got pregnant. So it's obviously not a for sure "if he cums in me I WILL get pregnant" but it raises the chance of it happening more than it already is because we have unprotected sex. I don't know what to do. Part of me is thinking about just letting him do it. At least once for the feeling of it. But I don't know. I just want some advice. And please don't just say "don't do it. Don't even think about it! Why would you do that?" Or anything like that please. That's not the kind of advice I'm looking for. I already know it isn't the smartest idea but the thought of him doing it is stuck in my mind and I don't know what to do.