Dear jilllou: A category 3 mammogram generally indicates that there is some uncertainty (although probably benign) as to the "abnormality." Appropriate follow-up depends somewhat on other factors - bloody discharge - for example and could range from a repeat mammogram in a relatively short time frame (3-6 months) to a visit to a surgeon. If this bloody discharge is spontaneous (comes out without sqeezing) and is unilateral (on one side), it needs to be evaluated regardless of the mammogram results.
Unless there's good evidence of infection, antibiotics may not accomplish much. For any given lump, there's a certain amount of judgement required, as to when and if biopsy should be done, and by what method. But when there is bloody discharge, it's generally necessary to get a specific answer why it's there; and that means some form of biopsy. That can mean removing the duct from which the blood is coming, or, if it's clear that there's a mass involved, removing or sampling that mass. By far the majority of instances of bloody discharge are due to something other than cancer. But it's on the list of possibilities, and needs to be ruled out.