My boyfriend and I had sex on november 17th and he didnt pull out and instead came inside me. Then around December 4th we had unprotected sex again and didnt pull out. I had breast tenderness a few days after the first time but it went away.I was also extremely nauseated and had horrible head and back aches. I've taken tests and they've come out negative for the first time. I still havent had a period. Could i be pregnant?