How Could I Have These Symptoms But A Negative Pregnancy Test?

Okay, so for one i have been getting hot flashes which i NEVER get. two, I have been feeling very nauseated. I am beginning to get tired all day long, i am suppose to be on my period but it is very light and bright red to dark red blood. I am having major cramping in my uterus but like I said, barely any blood. My lower back is KILLING me for some reason. I have been getting very bad frequent headaches...but I took a test today and it came out negative. And I have barely any soreness in my breasts. Could I still be pregnant or am I just going through some crazy stage of hormones of some sort at the age of 22? I have a normal 28 day cycle on my BC with heavy menstrual usually. All cramps and bleeding. Never have i gotten nauseated, hot flashes or anything else i am getting. Someone had once said you could have light bleeding due to conception. i'm not sure. this is all just weird to me and i am confused lol. And also, one of my aunts had full blown periods during her pregnancy up till she was 7 months pregnant.