What Are The Chances Of Getting Pregnant Inspite Of Being On Nuvaring?

Hi. This morning, my bf and I had unprotected intercourse. I normally take my ring out for intercourse (my PCP said it is OK to do so, as long as I reinsert it within 3 hours) and for some reason, it slipped my mind to put my ring back in after. We just realized it, when we saw my ring next to the bed when I came home from work this evening. That means it has been out of my vagina for about 16-18 hours after intercourse (and ejaculation). Is there a chance of being pregnant? Normally I would be running to the pharmacy for EC, but I was wondering how possible or how high of a risk pregnancy actually is. *I ve been using the same method of BC every month for the last 4 years with no issues (nuvaring) * I m on week 3 of my cycle, with the day I m actually supposed to take my ring out (start of week four and menstruation) being scheduled in only 2 more days from now *I reinserted my ring as soon as I seen it was out (about 16-18 hours later). I don t want to waste my time and money on EC, if my period is going to show up like normal in 4 days from now, but I m also not sure when my body ovulates, and the ring was out for more than the 3 hours that is recommended. Thank you in advanced