Mastitis

I had mastitis with my second child and the antibiotics worked pretty quickly. I now have it with my 3rd child who is 3 weeks old. They started an antibiotic on Friday afternoon but I am not getting better. My fever is actually getting worse. It was 103 at the last check. I have also been nursing, pumping, warm compressions, showers, massage and drinking a ton. Any suggestions on something else to do or how long an antibiotic can take to kick in?  Thanks!  This is truly the most painful thing.