Nuva Ring and Pregnancy?

[omgz-mandaaa.livejournal.com]

Hello I have a question concerning my nuva ring cycle. I started Nuva Ring the sunday after my period, Aug. 10th. Kept it in for 3 weeks, but took it out the SATURDAY August 30th. My period came in time, okay no problems. Put it in the following Sunday September 7th. The first month my boyfriend never came inside me because it was the first month. However this month of course, he has. A friend informed me that I should have taken it out the Sunday August 31st instead of Saturday. I'm a little scared that I have messed up the days and/or have the possibility of being pregnant. I know there's no certainty here, but could someone explain to me the chances of this happening? Thank you.