I'm on the pill, and have not missed a dose. I have been on the pill for years. My last period was on May 11. I had sex on May 21, and experienced light brown spotting 3 days later. The spotting lasted 4-5 days. I expected my period last week, and all it was was very light brown spotting again and some minor cramping. I took a HPT 14 days after sex and 19 days after sex, and both were negative. Could I be pregnant?