What Is Causing My Abdominal Cramps And Bloating With Nausea?

my last period was 23rd July, and the last 2 weeks i've had terrible cramps which i assumed were 'period pains'. i've had a swollen stomach, and have been throwing up (but have also been sick, as has the rest of the family) Yesterday i started to bleed, but it is a orangey colour and very watery. It also feels very heavy, and my stomach is not getting any smaller, and the cramps are not easing. I have taken 2 pregnancy tests, both were negative.