What is Wrong? I'm in so much pain?

i am a 19-year-old female and need some help. my breasts have been aching horribly (not normal menstrual breast aches) for almost two weeks now and my body has been overly sensitive and i became nauseous/exhausted easily. I was a little late on my period, but only by a few days. this morning, i woke up in writhing pain. i realized that i had started my period. i have been doubled over since 7am and am having surges of almost unbearable pain in my uterus and intestines. i have had diarrhea and a heavy blood flow. I am afraid and need some help figuring out what's going on. thanks in advance, i promise im not being dramatic... there is a great deal of pain.