Hello, I Have Been Having Period Like Cramps In My

Hello, I have been having period like cramps in my lower back and my boobs/nipples are sore and the nipples have turned a whitish color and I'm very bloated. My period is not due until the 13th of this month. I have been having sleeping problems and other problems as well. I took a pregnancy test but it was negative but I've been told that I took it too early. Could I still be pregnant? Or what else could it be?