Boyfriend wants to cum in me

So my boyfriend and I are still fairly new into our relationship and we haven’t had sex yet. We talk about it a lot and tell each other our fantasies and what turns us on. His biggest turn on is cumming inside instead of pulling out or using condoms. It’s not that I don’t love the idea of it, but I don’t use any type of birth control except for condoms. I don’t like the idea of putting chemicals in my body to prevent pregnancy. My younger sister has been using pills since she was 14 and is now 25 and having trouble conceiving, not sure if it’s related but it still scares me. Anyway I really just needed to vent a little, not sure what to do about this situation. I’m having surgery in my stomach tomorrow and can’t risk getting pregnant for at least 18 months. Guess my boyfriend’s fantasy will just have to stay a fantasy for a while. Thanks for reading. Opinions are welcome 🙏