Period or not?

Has anyone had an experience where "period" came a week and a half early, it was three days only and only enough to fill up two panty liners each day, none at night, and then been pregnant? My question is I feel so nauseated now and took a pregnancy test two days ago while on my "period" that was negative. I'm almost positive it was my cycle, but how long will it take for a positive test to happen after that sort of thing if I were?