help with my period

 so my period came a day early at night time and it was only a couple spots.  after that it stopped & continued the next day in the afternoon.  my period was pink and brown in Lester for six days.  usually my period is superheavy and makes a mess.  it’s been a week since then and my nipples are sensitive but not really darker. ive been having cramps & back pain also. what could be happening?