I had sex on the 4th and my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period app</a> is saying I'll be fertile from the 6-12 ovulating on the 11th.

when I had sex, I used a condom but my partner pulled out without holding the base of the condom so it rolled up a bit and im very paranoid that it got inside me so I took a plan b within 24 hours. today, i feel really nauseous. I had sex before being fertile and ovulating and he didn't necessarily cum in me. should I be worried about being pregnant? and could the nausea just be a plan b side effect?