Im 18yrs old on birth control (loestrin24) and have sex regularly. For unknown reasons I havent had a period in 4 months but every time i take a pregnancy test it comes out negative. For about two weeks now Ive had sore nipples,feeling nauseous, a lump below my stomach, severe cramping &stomach pains, diarrhea , weight gain and odorless black liquid coming from my vagina. The last time i took a pregnancy test was about a month ago. Should i take another? Whats wrong with me?