I'm 19 years old and have been sexually active with my fiance. My last period was in January, I completely missed February, and now I am a couple days late in March. I have taken tests at home and all were negative, even though I have been having symptoms like nausea, breast tenderness, light headedness. I am now started to feel pains on the right side of my abdomen. I have a doctors appointment this Friday, but I would like to have a few answers before then. What could be wrong with me?