Why do I get nausea when my boyfriend s in me?

Sometimes but not often, during while my boyfriend s inside of me i get nausea. After he is done, I feel nausea and have the feeling of throwing up but I don't. I pulled the Nuva ring out the week before the 29th. I just had a period July 25th and am due again August 25th. Then I neva put the ring back in. Is it possible i am pregnant or not?