Is it normal for a partner to have a 'nature knows' approach to protection?

To be honest, your partner saying "nature knows" is pretty indifferent and irresponsible. I mean, it’s not nature, it’s science that knows in this situation. Maybe their ease will make things even harder for you in the future. I think you should be clear and say directly; this relationship can't continue without a condom or birth control. It's your body after all, the decision is yours.

I don't find this 'natural method' thing silly at all. My aunt has been protected like that for years, and there have never been any issues. It seems to work when calculated correctly. Maybe you are just unnecessarily anxious?

That's not how it works. It's very difficult to accurately calculate dangerous days. The body doesn't always function on the same cycle. For example, if you experience stress, ovulation might be delayed by 1-2 days. This is a very risky situation and could have serious consequences. The most sensible thing to do is to determine a method of protection. Be sure to consult an expert for accurate information and tests.

Yes, I learned a lot from the comments, thank you. But let me add this, my partner actually loves me; it's just that they're very 'comfortable' about it, let's say. Now I'm thinking about talking more seriously 😳

What's this reasoning like 'nature feels' or whatever? When having a child, are they going to say 'nature takes care of it anyway'? Honestly, this is just self-deception 😂