Could I be pregnant?

Stephanie • Hi
So I usually have periods that last for about 5-7 days, however this one only lasted for two days but was just as heavy as my normal period would be. After the second day it just abruptly stopped.. I thought maybe it would come back but it never did. 
I felt as if I was having a lot of pregnancy symptoms before my period came so I took 3 pregnancy tests before my expected period and all of them came out to be negative. 
Now that my period is gone, I've been feeling nauseous for the past few days and have been vomiting at random times of the day. I've also been having stomach cramps as well as back pain and sore breasts. 
I'm just really confused because I bled pretty heavily - not spotting, and I got three negative test results. Should I test again in a week ? Or is my period just acting up on me? 
I don't take oral contraceptives and I haven't changed anything about my diet or lifestyle. 
I'm so confused!