smelling "CheezIts" made me feel sick.

I am in college, I am 20 years old. I am one week late on my period. My periods are very regular, and I am not on birth control. I feel nauseous after I eat. My nipples are very sore, but they are not darker and my boobs aren't bigger. I have constant headaches. I seem to be hungry all the time now! I don't make constant bathroom breaks. I took a pregnancy test last week and it was negative, though. Last night, my boyfriend was eating "CheezIts" and smelling them made me feel sick. I ate a piece of cheese and felt very sick last night! I don't know what to think! HELP ME.