Paranoia..

I had sex with my bf Nov 2nd and took a plan B the same day. My cycle came on November 13th and lasted until the 18th of November. We had sex again on November 22nd for a few minutes it was unprotected and then he put a condom on. A few days later I started feeling nauseous and I’m still nauseous a few weeks later. I’ve taken a few pregnancy tests and they’ve all come up negative. Could I still be pregnant or am I overthinking?