I'm 19 years old & have my periods every month. However, I do not have a specific cycle, as mine changes every month. March 5th 2011 was the last period I had & I have not gotten one since. I have taken 3 hpts, as well as a blood test & they all came back negative. However, I have every symptom of pregnancy. My mom even thinks I'm pregnant as my breasts have gained a cup size in the last month, as well as the colour around the nipple has darkened. I have also gained about 15-20 pounds in the last 2 months, all showing only in my abdomen. Please let me know if it's possible I still could be pregnant & if not, what else could be causing this?