False positive?

My husband and I recently decided to start trying to conceive. I have only been of the nuvaring for one month and my period is only 2 days late and I've been having my typical period symptoms. I figured it was just my body getting used to being off birth control, but tonight I took a pregnancy test and it came out positive. How possible is a false positive and should I retest? I didn't expect anything to happen so quickly, so we're both just in complete shock and aren't even sure what to think.