Late period after taking plan b and 4 negative tests

I slept with a scumbag who took off the condom without my knowledge. He told me a day and half later and I took plan b ASAP. I had just finished my period so I’ve now waited around 4 weeks since we had sex on the 3rd and I took the pill on the 4th of November. I bled for two days exactly a week after I took the pill. My period had ended just a few days before. Now, I am 4 days late but I’ve taken four pregnancy tests that have all come out negative. What can this mean? I have lost my appetite a little and tend to feel nauseous at times. Has anyone experienced anything similar? I really don’t want to be pregnant :(