Mastitis or thrush

On Thursday night I woke up with pain like a blocked duct. I put a warm compress on and nursed and pumped. I was in so much pain all night and seemed to be getting worse. My nipple hurts (might also have a milk blister, have a couple white bubbles) my breast hurts when I have anything pressed up against it, feel a burning pain every once in awhile. On Friday I also had a mild fever and body aches and pains. My OB and lactation lady said sounded like mastitis and prescribed antibiotics. I just started the meds last night because my fever went away on Saturday and thought I was on the mend. The pain is too much when nursing and my breast has a red rash so I gave in to meds. Read so much online that I am not sure if it's thrush or mastitis. Baby has no white stuff in mouth. Anyone have any advice or experience?