Opinions please!!

Okay so my SO and I had sex 10 days ago. The condom broke but he didn't ejaculate. I'm really scared about pre cum so I took a pregnancy test 3 days ago, a week after what would have been the date of conception like the pregnancy test said I could, and it came back negative. It calmed me down a lot but now I'm starting to feel super nauseous. Idk if that's because of my birth control (which is basically useless since I'm taking antibiotics right now) or because I am actually pregnant. Could I be pregnant? We had sex a day before my period was supposed to begin, but I missed 2 pills at the very beginning of the month because of pharmacy problems, so could it be because of the missed pills? Or could I be pregnant? HELP!!