I am now six days late on my period. I have been experiencing severe pain in my lower back for the last three days, extreme fatigue, massive mood swings, and I noticed very little bright red blood when I wiped after going to the bathroom an hour ago. I also started experiencing pain in my lower left side this morning and nausea. I have had a headache for the last week. I took a pregnancy test three days ago and this morning, both were negative. The thing that worries me the most is I had tubal ligation 7 years ago. Could I be experiencing an tubal pregnancy?