Hi I Am 3 Weeks Post Op Robotic Sacrocolcopexy, Rectocele

Hi I am 3 weeks post op robotic sacrocolcopexy, rectocele repair, hysterectomy, bladder sling. The incision at my belly button is infected. I have been taking keflex 500mg tid since thursday (3 days). The area is still extremely painful, very red and still has puss that will drain periodically. Do I need a stronger antibiotic or is it normal for it to be taking this long to improve. Thank you for your help.