Wondering if I'm pregnant?

Lindsay • Married 8-9-14 Baby #1 Born 1-26-16
I've had a few pregnancy symptoms, VERY moody, mild cramps, sore/full breasts, headaches, tired. Yesterday I was very sick all day- vomiting and a little diarrhea, thought this could be a good sign because I'm never sick! I slept a lot last night into this morning and woke up feeling not nauseous anymore. Took a pregnancy test this afternoon (early detection) but came up negative. 
I'm CD 23, AF due 12/31. 
Could I still be pregnant, maybe it's still a little too early to test? What about the nauseous one day and not the next- is this common in early pregnancy?