I Have A Question About My Girlfriend Possibly Being Pregnant

I have a question about my girlfriend possibly being pregnant.I need help finding out more information about the situation right now please help. We had unprotected sex during her most fertile days. I came inside of her 2 times on the 19th. I didn't tell her that i came but that was my first time ever that i came inside of her. 2 days later on the 21st i came again but this time i told her. She later found out that her fertile days were between the 17 and the 26. The main day that she was ovulating was the 21st. She's okay if we have a baby the only reason why she doesn't want to is because of her family and mainly because she wants to finish school 1st (college) She suppose to be getting her period by the 3rd so 2 days from now but today we went to buy a home-pregnancy test and it came out negative(We bought the cheapest one though) She says her head really hurts sometimes and she has nauseas but she has always been like that but now she says that sometimes she feels like throwing up too and feels something in her stomach. From the 19 till now i already came inside of her 6 times because i really do want a baby. So could she still be pregnant??? PLEASE HELP