Pregnancy scare

I lost my virginity on February 10th at 2:00am and we used two condoms. I also was not ovulating at the time. I started ovulating February 15th. During the intercourse he would keep pulling out to make sure the condom didn’t break. Eventually he took off the first condom and put on the other. He stopped soon after because he thought the condom was about to break and that was his last one. He also told me he had not came yet. I took a plan b just to be safe around 3:00pm the same day. The next couple days I woke up with a very minor headache but it only lasted about 5 minutes. Other than that I had no symptoms. On February 15th i started experiencing breakthrough bleeding which is a side effect of plan b and also a symptom of pregnancy. I took a pregnancy test February 17th and 20th and they both came out negative. Is it possible i could be pregnant?