I Had An IUI 12 Days Ago. I Have Been

I had an IUI 12 days ago. I have been nauseous for a week, and had some spotting over the weekend (10 days post IUI). I had a blood pregnancy test today and it came back negative. Is there a chance it's too early? I am a 28 day cycle girl, and never have spotting between periods. Also I have never had nausea like this before. I had 4 good sized follicles prior to the procedure.