This medicine is cefuroxime which is in the cephalosporin group of antibiotics. it is a broad spectrum antibiotic. The antibiotic needs to be completed to have the full benefit. You need to be rinsing, brushing and flossing with gentle, but effective care. Warm salt water is an effective rinse. Often some increase in sensitivity can occur as the gums heal. I do not know the condition of your gums when you started the antibiotic. I suggest you discuss this with your doctor. Have you had a cleaning or are you scheduled for more cleaning or a deep under the gum cleaning? Puss on the gums is a sign of infection. You may need an additional perscription. Rinse such as chlorhexidine may be needed to help tissue healing. Please consult your dentist. Some anti-inflammartory medicine may help healing and make you feel better.