I am a 20 year old female. I had my period on June 20th. Starting 4days ago <july 5> I was having really sharp pains from my belly button down on my right side it felt like someone was stabbing me with a knife the pain hasn't stopped it just eases then gets worse. Starting yesterday I was hurting really bad in my pelvic and rectum when I would cough talk set walk or bend. The pain started easily and now it will go from light pain to sevre where it feels like I am in labor like I was with my two children but a pregnancy test is negative what could this be?