Am I unable to conceive?

My SO & I aren't TTC but we only use the pullout method (most of the time, don't judge!) but I was just thinking, how is it that I haven't got pregnant? We've had multiple slip ups & my SO has finished inside me a handful of times. Like I said, we're not currently TTC but I'm worried that when we are ready, I won't be able to. How do I find out? Or is it just harder to get pregnant than it seems? Is this a normal worry or am I jumping the gun here 😩