Pregnant or not

HI, 

I had sex around two months ago. I used protection except for one time but my bf did not cum in me. I had some pregnancy symptoms and decided to take a home pregnancy test 3 weeks after I had sex. It came out negative. It has been two months since I had sex and im having symptoms. I have missed two periods and im having little brown discharge. This could be cause I had very little sleep the first month thanks to finals and stress but i dont know. I have felt a little dizzy and nauseated. My smell was really sensitive one day. Sometimes i feel tired but not all the time. And one day my pelvis started to hurt but it was only one day I also got a leg cramp. These symptoms go on and off. I want to know if there is any other reason(s) beside pregnancy that could be causing all of this...Please and thank you!