My period started on the 5th December and ended on the 9th December. It's been 4 days since I ended my period and I had brown spotting on the 10th December and it lasted for a couple of minutes then it disappeared since that I had started this morning feeling very nausea ( up and down waves ), and very sore boobs and just not normal me. But my next period is on the 30th December??

What kind it be??