How do tests at the doctor’s work?

So, I’ve only ever had sex once (my first time) a week ago, and he used a condom and everything, but I went to the doctor today to get antibiotics for a UTI caused by my kidney stones and had to take a urine test. Even if it isn’t a pregnancy-test specific test, can doctors tell if you’re pregnant? Are they obligated to tell you even if you don’t ask? I know the chances of me being pregnant are very low, but the PA that came in at the end of my appointment scared me a little, and I was worried that she didn’t want to say anything with my guardian there.