Could Delayed Periods Be Due To Nuvaring?

I used the missing for about 4 1/2 months before I decided to come back off it in November. I had one period that lasted 9 days and I have yet to receive a period for the month of January. It is now February. Can the nuvaring delay periods or cause me not to ovulate for a certain amount of time? I have been having unprotected sex. Is there a great possibly of pregnant even though I ve tested negative on hpt s?