Mastitis Help?!?!?/Expressing

I am expressing breastmilk (using double pump from hospital) as my twins were born premature at 31 weeks and are in special care. Developed mastitis in right breast still managing to express same amounts as before and I am on antibiotics, does anyone have any advice as to how long before I feel better as at mmoment feeling really S**T. Also what amounts do other girls manage to expres? i am getting 100ml off each breast every 4 hours.