10 days late...

for the past year I have been every 27 days with day 26 being pinkish spots. and now I'm 37 days.. I've taken two test and still neg. I have two boys 7&2 and it was approx 6 wks when I found out with them and positive test instantly. I don't know why this would be negative if my other two showed up so soon? no nausea but really bad headaches a little moody and three days ago I had super high cramps worse then PMS cramps for about three hrs then went away and haven't came back. Dr told me today to wait two more wks before taking another one. really?? lol anyone else in the same boat?? if I put in last cycle it shows to be 5 wks along....