Could I be pregnant? Freaking out over here

I had sex with my boyfriend at the end of my period, around Day 4/5. He wore a condom during sex, and when he was ready to cum he pulled out and came on my chest & stomach. I think a little bit of the cum moved from my stomach and leaked into my vagina since I was sitting on an incline.

I had light brown spotting about 2 weeks after this happened. I took a pregnancy test on Day 28 of my cycle (when I should be getting my period) and it was negative. Have been feeling a little nauseous but not sure if from stress & worry.

I am freaking out, is it likely that I am pregnant?