Letting my partner finish inside me + Birth Control

My boyfriend and I had sex and I let him finish inside me. I've been on the pill for a while now but I'm having major concerns. 
1. The day I had sex was the day I was supposed to start a new pack of birth control pills. I had sex around 3pm but don't normally take my pill around 10pm. So I'm concerned. 
Could there be a possibility that my body could have been unprotected? 
2. Ever since that day I've been feeling nauseous. 
Could that be because I'm having a negative reaction to the sperm in my body? 
It's only been a week so I know it's too early for it to be signs of pregnancy. 
Does anyone know what this could be? Why I feel so weak and nauseous?
I've r