I have extremely painful stomach cramps and have done for four days, i had a fever on day one and have diarrhoea occasionally with blood?

Needs evaluation now: I don't know if you've traveled recently but any diarrhea with a fever or diarrhea with blood needs evaluation by a doctor. This is because once the lining of the gut (bowels) is breached -as evidenced by the blood- whatever germs or pathogens there have direct access to the blood stream and can cause problems. These symptoms have gone on for too long also to be considered 'self-limited'.