Chances of being pregnant on nuvaring?

I just started the nuvaring this month and it hasn't stopped my ovulation. We've had sex a few times and it apparently came out when I was using the bathroom sometime last night. The only reason I knew it wasn't there was I've been checking it everyday. I just put a new one in, but what are the chances I could get pregnant? I'm super nervous. Has anyone had any experiences similar to this?