Could i be pregnant and not know?

I've been having really bad nausea past 2 months but this moth it's everyday and I'm popping zofran like crazy. my breasts are super sensetive. I got my period 2 days early and it ended 3 days earlier than my normal length, it was lighter than normal. Today I'm having severe pain in abdomen around the belly button area and back where it would be in front and it feels like I'm having contractions. I took a test this afternoon it was negative. I just have no clue. when I was pregnant with my daughter my POTS acted up and I had hyper emesis the entire pregnancy. thanks for input.