What Causes Delayed Periods With Sore Breasts And Back Pain?

my last period was 3/29. I was suppose to get my period 4/29 and I didn't. I have been super nausea, back pain,sensitive breasts, sensitive to smells, butterfly feeling in my stomach. I took a pregnancy test and it was negative. I was 14 days late on my period. On Friday I went to the bathroom and there was little blood but that was it. An hour later I went to the bathroom again and absoultely nothing. Then throughout the day it would come and go. Same all through the weekend? Is it a miscarriage or my period?