pregnancy test fail or not?

I took a pregnancy test 4 days before my period, and when I first looked at the test it came out to be negative... however today when I looked at it, the same one it was a positive result....it may be have been positive the entire time because I didn't wait 10 minutes like it said on the box..: I got upset and put it away .... I'll test again in few days if AF doesn't come , but I really feel like it's coming ... I've been cramping on and off for a week