Hospital Pregnancy Test

Hey, everybody. I'm fairly new here, and this is my very first post. I just wanted to see if any of you have had the following experience. I was supposed to start AF on Oct 8th. On that same day, I ended up going to the hospital for serious back and pelvic pain. They did a urine pregnancy test to see if I was pregnant (to make sure they didn't give me certain meds in case I was), and that came back negative. However, AF has still not appeared, and I realized today that I had some weird, light spotting a few days before my period. Is it possible for the hospital test to be wrong?