HELP!

Bee

So, my period is 15 days late, I've taken 3 pregnancy tests all 3 have said negative, my boobs are very swollen, large, painful and hot & my heads pounding. My belly is swollen and I'm having bad cramps. I was gonna wake up and schedule an appointment today but when i woke up and I'm bleeding as the day has went on the bleeding is heavier. Its dark too, could this be something serous or is it just my period?