should i be nervous?

okay so usually like a week before i start i have cramps and all that jazz but i'm suppose to start today but haven't had anything. my boyfriends freaking out thinking i'm pregnant, i am a freshman in college and have midterms all month and i am trying to think of that could of pushed it back...i do not want to have a kid this early. i've had back pains and sharp pains throughout my chest middle stomach...i refuse to take a pregnancy test because i am scared of getting a result i don't want. what should i do?