Could my birth control have failed?

I used to be on birth control over 6 months ago and I recently put nuvaring in exactly a week after my period. My boyfriend and I had the night i put it in and he finished in me. I read that it can take up to 7 days for nuvaring to be effective. We have had a few more times during the past month and he finished in me each time. Then I left it in a week too long so I'm wondering if it was ineffective that week as well. I have missed my period and my are very sore. Before I put nuvaring in, my periods were pretty irregular so I'm not sure how my cycle has been. I'm kind of tired and have cramps. I'm wondering if perhaps I could be pregnant. Any answers would help! Thanks!