My last period was 7th of Dec. I usually get my periods every 28 days. This would make me due my period on Jan 3rd. It hasn't arrived. My breasts are very soar since the 3rd. They feel heavy and swollen. Normally they would only hurt slightly and just the day before I'd get my period. Today the end of my tummy is achy. I done a urine pregnancy test on the 3rd and again this morning. Both were negative. Any ideas?